diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 00000000..bcbd94d4
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,159 @@
+name: build
+
+on: [push, pull_request]
+
+env:
+  # color output for pytest and tox
+  PYTEST_ADDOPTS: "--color=yes"
+  PY_COLORS: 1
+
+jobs:
+  test:
+    name: Test - ${{ matrix.config.python }} - ${{ matrix.config.os }}
+    runs-on: ${{ matrix.config.os }}-latest
+
+    strategy:
+      matrix:
+        config:
+          - os: ubuntu
+            python: 3.5
+          - os: ubuntu
+            python: 3.6
+          - os: ubuntu
+            python: 3.7
+          - os: ubuntu
+            python: 3.8
+          - os: macos
+            python: 3.7
+          - os: windows
+            python: 3.7
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Python ${{ matrix.config.python }}
+        uses: actions/setup-python@v1.1.1
+        with:
+          python-version: ${{ matrix.config.python }}
+      - name: Set pip cache (Linux)
+        uses: actions/cache@v1
+        if: startsWith(runner.os, 'Linux')
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements/*') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+      - name: Setup pip cache (macOS)
+        uses: actions/cache@v1
+        if: startsWith(runner.os, 'macOS')
+        with:
+          path: ~/Library/Caches/pip
+          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements/*') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+      - name: Setup pip cache (Windows)
+        uses: actions/cache@v1
+        if: startsWith(runner.os, 'Windows')
+        with:
+          path: ~\AppData\Local\pip\Cache
+          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements/*') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+      - name: Install locale (Linux)
+        if: startsWith(runner.os, 'Linux')
+        run: sudo locale-gen fr_FR.UTF-8 tr_TR.UTF-8
+      - name: Install pandoc
+        uses: r-lib/actions/setup-pandoc@v1
+        with:
+          pandoc-version: "2.9.2"
+      - name: Install tox
+        run: python -m pip install -U pip tox
+      - name: Info
+        run: |
+          echo "=====  PYTHON  ====="
+          python --version
+          echo "=====  PANDOC  ====="
+          pandoc --version | head -2
+      - name: Run tests
+        run: tox -e py${{ matrix.config.python }}
+
+
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Python
+        uses: actions/setup-python@v1.1.1
+        with:
+          python-version: 3.6
+      - name: Set pip cache (Linux)
+        uses: actions/cache@v1
+        if: startsWith(runner.os, 'Linux')
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ hashFiles('requirements/*') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+      - name: Install tox
+        run: python -m pip install -U pip tox
+      - name: Check
+        run: tox -e flake8
+
+
+  docs:
+    name: Build docs
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Python
+        uses: actions/setup-python@v1.1.1
+        with:
+          python-version: 3.6
+      - name: Set pip cache (Linux)
+        uses: actions/cache@v1
+        if: startsWith(runner.os, 'Linux')
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ hashFiles('requirements/*') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+      - name: Install tox
+        run: python -m pip install -U pip tox
+      - name: Check
+        run: tox -e docs
+
+
+  deploy:
+    name: Deploy
+    needs: [test, lint, docs]
+    runs-on: ubuntu-latest
+    if: ${{ github.ref=='refs/heads/master' && github.event_name!='pull_request' }}
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Python
+        uses: actions/setup-python@v1.1.1
+        with:
+          python-version: 3.7
+      - name: Check release
+        id: check_release
+        run: |
+          python -m pip install pip --upgrade
+          pip install poetry
+          pip install githubrelease
+          pip install --pre autopub
+          echo "##[set-output name=release;]$(autopub check)"
+      - name: Publish
+        if: ${{ steps.check_release.outputs.release=='' }}
+        env:
+          GITHUB_TOKEN: ${{ secrets.GH_TOKEN }}
+          PYPI_PASSWORD: ${{ secrets.PYPI_PASSWORD }}
+        run: |
+          git remote set-url origin https://$GITHUB_TOKEN@github.com/${{ github.repository }}
+          autopub prepare
+          poetry build
+          autopub commit
+          autopub githubrelease
+          poetry publish -u __token__ -p $PYPI_PASSWORD
diff --git a/.travis.yml b/.travis.yml
index af3a6ca8..c0637a7f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,15 +11,15 @@ env:
   matrix:
     - TOX_ENV=docs
     - TOX_ENV=flake8
-    - TOX_ENV=py35
-    - TOX_ENV=py36
+    - TOX_ENV=py3.5
+    - TOX_ENV=py3.6
 matrix:
   include:
     - python: 3.7
       sudo: true
       dist: xenial
       env:
-      - TOX_ENV=py37
+      - TOX_ENV=py3.7
 addons:
   apt_packages:
     - pandoc
diff --git a/docs/conf.py b/docs/conf.py
index 53171646..fc49975a 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -61,7 +61,7 @@ html_show_sourcelink = False
 
 def setup(app):
     # overrides for wide tables in RTD theme
-    app.add_stylesheet('theme_overrides.css')   # path relative to _static
+    app.add_css_file('theme_overrides.css')   # path relative to _static
 
 
 # -- Options for LaTeX output -------------------------------------------------
diff --git a/docs/themes.rst b/docs/themes.rst
index a2332615..86a754bc 100644
--- a/docs/themes.rst
+++ b/docs/themes.rst
@@ -242,7 +242,7 @@ as the name of the metadata field, except in all-lowercase characters.
 For example, you could add a field called `FacebookImage` to your article
 metadata, as shown below:
 
-.. code-block:: markdown
+.. code-block:: md
 
     Title: I love Python more than music
     Date: 2013-11-06 10:06
diff --git a/pelican/readers.py b/pelican/readers.py
index 8174aa79..8c108510 100644
--- a/pelican/readers.py
+++ b/pelican/readers.py
@@ -696,7 +696,7 @@ def path_metadata(full_path, source_path, settings=None):
             # Enforce a trailing slash when checking for parent directories.
             # This prevents false positives when one file or directory's name
             # is a prefix of another's.
-            dirpath = os.path.join(path, '')
+            dirpath = posixize_path(os.path.join(path, ''))
             if source_path == path or source_path.startswith(dirpath):
                 metadata.update(meta)
 
diff --git a/pelican/tests/support.py b/pelican/tests/support.py
index 8a22052e..e52bc0ae 100644
--- a/pelican/tests/support.py
+++ b/pelican/tests/support.py
@@ -160,6 +160,19 @@ def locale_available(locale_):
         return True
 
 
+def can_symlink():
+    res = True
+    try:
+        with temporary_folder() as f:
+            os.symlink(
+                f,
+                os.path.join(f, 'symlink')
+            )
+    except OSError:
+        res = False
+    return res
+
+
 def get_settings(**kwargs):
     """Provide tweaked setting dictionaries for testing
 
diff --git a/pelican/tests/test_cache.py b/pelican/tests/test_cache.py
index cc5218b7..564f1d31 100644
--- a/pelican/tests/test_cache.py
+++ b/pelican/tests/test_cache.py
@@ -1,17 +1,11 @@
 import os
 from shutil import rmtree
 from tempfile import mkdtemp
+from unittest.mock import MagicMock
 
 from pelican.generators import ArticlesGenerator, PagesGenerator
 from pelican.tests.support import get_context, get_settings, unittest
 
-try:
-    from unittest.mock import MagicMock
-except ImportError:
-    try:
-        from mock import MagicMock
-    except ImportError:
-        MagicMock = False
 
 CUR_DIR = os.path.dirname(__file__)
 CONTENT_DIR = os.path.join(CUR_DIR, 'content')
@@ -131,7 +125,6 @@ class TestCache(unittest.TestCase):
         self.assertEqual(uncached_pages, cached_pages)
         self.assertEqual(uncached_hidden_pages, cached_hidden_pages)
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_article_object_caching(self):
         """Test Article objects caching at the generator level"""
         settings = self._get_cache_enabled_settings()
@@ -162,7 +155,6 @@ class TestCache(unittest.TestCase):
         """
         self.assertEqual(generator.readers.read_file.call_count, 6)
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_article_reader_content_caching(self):
         """Test raw article content caching at the reader level"""
         settings = self._get_cache_enabled_settings()
@@ -185,7 +177,6 @@ class TestCache(unittest.TestCase):
         for reader in readers.values():
             self.assertEqual(reader.read.call_count, 0)
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_article_ignore_cache(self):
         """Test that all the articles are read again when not loading cache
 
@@ -212,7 +203,6 @@ class TestCache(unittest.TestCase):
             generator.readers.read_file.call_count,
             orig_call_count)
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_page_object_caching(self):
         """Test Page objects caching at the generator level"""
         settings = self._get_cache_enabled_settings()
@@ -238,7 +228,6 @@ class TestCache(unittest.TestCase):
         """
         self.assertEqual(generator.readers.read_file.call_count, 1)
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_page_reader_content_caching(self):
         """Test raw page content caching at the reader level"""
         settings = self._get_cache_enabled_settings()
@@ -262,7 +251,6 @@ class TestCache(unittest.TestCase):
         for reader in readers.values():
             self.assertEqual(reader.read.call_count, 0)
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_page_ignore_cache(self):
         """Test that all the pages are read again when not loading cache
 
diff --git a/pelican/tests/test_generators.py b/pelican/tests/test_generators.py
index 5dd5c3ec..332d7e78 100644
--- a/pelican/tests/test_generators.py
+++ b/pelican/tests/test_generators.py
@@ -1,22 +1,17 @@
 import locale
 import os
+import sys
 from shutil import copy, rmtree
 from tempfile import mkdtemp
+from unittest.mock import MagicMock
 
 from pelican.generators import (ArticlesGenerator, Generator, PagesGenerator,
                                 PelicanTemplateNotFound, StaticGenerator,
                                 TemplatePagesGenerator)
-from pelican.tests.support import get_context, get_settings, unittest
+from pelican.tests.support import (can_symlink, get_context, get_settings,
+                                   unittest)
 from pelican.writers import Writer
 
-try:
-    from unittest.mock import MagicMock
-except ImportError:
-    try:
-        from mock import MagicMock
-    except ImportError:
-        MagicMock = False
-
 
 CUR_DIR = os.path.dirname(__file__)
 CONTENT_DIR = os.path.join(CUR_DIR, 'content')
@@ -198,7 +193,6 @@ class TestArticlesGenerator(unittest.TestCase):
         return [[article.title, article.status, article.category.name,
                  article.template] for article in articles]
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_generate_feeds(self):
         settings = get_settings()
         settings['CACHE_PATH'] = self.temp_cache
@@ -218,7 +212,6 @@ class TestArticlesGenerator(unittest.TestCase):
         generator.generate_feeds(writer)
         self.assertFalse(writer.write_feed.called)
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_generate_feeds_override_url(self):
         settings = get_settings()
         settings['CACHE_PATH'] = self.temp_cache
@@ -334,7 +327,6 @@ class TestArticlesGenerator(unittest.TestCase):
         categories_expected = ['default', 'yeah', 'test', 'zhi-dao-shu']
         self.assertEqual(sorted(categories), sorted(categories_expected))
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_direct_templates_save_as_url_default(self):
 
         settings = get_settings()
@@ -352,7 +344,6 @@ class TestArticlesGenerator(unittest.TestCase):
                                  template_name='archives',
                                  page_name='archives', url="archives.html")
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_direct_templates_save_as_url_modified(self):
 
         settings = get_settings()
@@ -373,7 +364,6 @@ class TestArticlesGenerator(unittest.TestCase):
                                  page_name='archives/index',
                                  url="archives/")
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_direct_templates_save_as_false(self):
 
         settings = get_settings()
@@ -398,7 +388,6 @@ class TestArticlesGenerator(unittest.TestCase):
         self.assertIn(custom_template, self.articles)
         self.assertIn(standard_template, self.articles)
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_period_in_timeperiod_archive(self):
         """
         Test that the context of a generated period_archive is passed
@@ -1022,7 +1011,6 @@ class TestStaticGenerator(unittest.TestCase):
         with open(self.endfile) as f:
             self.assertEqual(f.read(), "staticcontent")
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_file_update_required_when_dest_does_not_exist(self):
         staticfile = MagicMock()
         staticfile.source_path = self.startfile
@@ -1032,7 +1020,6 @@ class TestStaticGenerator(unittest.TestCase):
         update_required = self.generator._file_update_required(staticfile)
         self.assertTrue(update_required)
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_dest_and_source_mtimes_are_equal(self):
         staticfile = MagicMock()
         staticfile.source_path = self.startfile
@@ -1045,7 +1032,6 @@ class TestStaticGenerator(unittest.TestCase):
         isnewer = self.generator._source_is_newer(staticfile)
         self.assertFalse(isnewer)
 
-    @unittest.skipUnless(MagicMock, 'Needs Mock module')
     def test_source_is_newer(self):
         staticfile = MagicMock()
         staticfile.source_path = self.startfile
@@ -1097,6 +1083,7 @@ class TestStaticGenerator(unittest.TestCase):
         self.generator.generate_output(None)
         self.assertTrue(os.path.samefile(self.startfile, self.endfile))
 
+    @unittest.skipUnless(can_symlink(), 'No symlink privilege')
     def test_can_symlink_when_hardlink_not_possible(self):
         self.settings['STATIC_CREATE_LINKS'] = True
         with open(self.startfile, "w") as f:
@@ -1104,40 +1091,29 @@ class TestStaticGenerator(unittest.TestCase):
         os.mkdir(os.path.join(self.temp_output, "static"))
         self.generator.fallback_to_symlinks = True
         self.generator.generate_context()
-        try:
-            self.generator.generate_output(None)
-        except OSError as e:
-            # On Windows, possibly others, due to not holding symbolic link
-            # privilege
-            self.skipTest(e)
+        self.generator.generate_output(None)
         self.assertTrue(os.path.islink(self.endfile))
 
+    @unittest.skipUnless(can_symlink(), 'No symlink privilege')
     def test_existing_symlink_is_considered_up_to_date(self):
         self.settings['STATIC_CREATE_LINKS'] = True
         with open(self.startfile, "w") as f:
             f.write("staticcontent")
         os.mkdir(os.path.join(self.temp_output, "static"))
-        try:
-            os.symlink(self.startfile, self.endfile)
-        except OSError as e:
-            # On Windows, possibly others
-            self.skipTest(e)
+        os.symlink(self.startfile, self.endfile)
         staticfile = MagicMock()
         staticfile.source_path = self.startfile
         staticfile.save_as = self.endfile
         requires_update = self.generator._file_update_required(staticfile)
         self.assertFalse(requires_update)
 
+    @unittest.skipUnless(can_symlink(), 'No symlink privilege')
     def test_invalid_symlink_is_overwritten(self):
         self.settings['STATIC_CREATE_LINKS'] = True
         with open(self.startfile, "w") as f:
             f.write("staticcontent")
         os.mkdir(os.path.join(self.temp_output, "static"))
-        try:
-            os.symlink("invalid", self.endfile)
-        except OSError as e:
-            # On Windows, possibly others
-            self.skipTest(e)
+        os.symlink("invalid", self.endfile)
         staticfile = MagicMock()
         staticfile.source_path = self.startfile
         staticfile.save_as = self.endfile
@@ -1147,8 +1123,18 @@ class TestStaticGenerator(unittest.TestCase):
         self.generator.generate_context()
         self.generator.generate_output(None)
         self.assertTrue(os.path.islink(self.endfile))
-        self.assertEqual(os.path.realpath(self.endfile),
-                         os.path.realpath(self.startfile))
+
+        # os.path.realpath is broken on Windows before python3.8 for symlinks.
+        # This is a (ugly) workaround.
+        # see: https://bugs.python.org/issue9949
+        if os.name == 'nt' and sys.version_info < (3, 8):
+            def get_real_path(path):
+                return os.readlink(path) if os.path.islink(path) else path
+        else:
+            get_real_path = os.path.realpath
+
+        self.assertEqual(get_real_path(self.endfile),
+                         get_real_path(self.startfile))
 
     def test_delete_existing_file_before_mkdir(self):
         with open(self.startfile, "w") as f:
diff --git a/pelican/tests/test_importer.py b/pelican/tests/test_importer.py
index 709086c0..76feb9ce 100644
--- a/pelican/tests/test_importer.py
+++ b/pelican/tests/test_importer.py
@@ -1,6 +1,7 @@
 import locale
 import os
 import re
+from posixpath import join as posix_join
 
 from pelican.settings import DEFAULT_CONFIG
 from pelican.tests.support import (mute, skipIfNoExecutable, temporary_folder,
@@ -448,5 +449,5 @@ class TestWordpressXMLAttachements(unittest.TestCase):
             self.assertEqual(1, len(locations))
             directory = locations[0]
             self.assertTrue(
-                directory.endswith(os.path.join('content', 'article.rst')),
+                directory.endswith(posix_join('content', 'article.rst')),
                 directory)
diff --git a/pelican/tests/test_readers.py b/pelican/tests/test_readers.py
index eb755338..de2a1b22 100644
--- a/pelican/tests/test_readers.py
+++ b/pelican/tests/test_readers.py
@@ -1,16 +1,10 @@
 import os
+from unittest.mock import patch
 
 from pelican import readers
 from pelican.tests.support import get_settings, unittest
 from pelican.utils import SafeDatetime
 
-try:
-    from unittest.mock import patch
-except ImportError:
-    try:
-        from mock import patch
-    except ImportError:
-        patch = False
 
 CUR_DIR = os.path.dirname(__file__)
 CONTENT_PATH = os.path.join(CUR_DIR, 'content')
@@ -125,7 +119,6 @@ class DefaultReaderTest(ReaderTest):
 
         self.assertDictHasSubset(page.metadata, expected)
 
-    @unittest.skipUnless(patch, 'Needs Mock module')
     def test_find_empty_alt(self):
         with patch('pelican.readers.logger') as log_mock:
             content = ['<img alt="" src="test-image.png" width="300px" />',
diff --git a/pelican/tests/test_rstdirectives.py b/pelican/tests/test_rstdirectives.py
index 36623fc4..6b733971 100644
--- a/pelican/tests/test_rstdirectives.py
+++ b/pelican/tests/test_rstdirectives.py
@@ -1,15 +1,8 @@
+from unittest.mock import Mock
+
 from pelican.tests.support import unittest
 
-try:
-    from unittest.mock import Mock
-except ImportError:
-    try:
-        from mock import Mock
-    except ImportError:
-        Mock = False
 
-
-@unittest.skipUnless(Mock, 'Needs Mock module')
 class Test_abbr_role(unittest.TestCase):
     def call_it(self, text):
         from pelican.rstdirectives import abbr_role
diff --git a/pelican/tests/test_server.py b/pelican/tests/test_server.py
index 68747001..307a3e10 100644
--- a/pelican/tests/test_server.py
+++ b/pelican/tests/test_server.py
@@ -25,11 +25,10 @@ class TestServer(unittest.TestCase):
         os.chdir(self.temp_output)
 
     def tearDown(self):
-        rmtree(self.temp_output)
         os.chdir(self.old_cwd)
+        rmtree(self.temp_output)
 
     def test_get_path_that_exists(self):
-
         handler = ComplexHTTPRequestHandler(MockRequest(), ('0.0.0.0', 8888),
                                             self.server)
         handler.base_path = self.temp_output
diff --git a/pelican/tests/test_settings.py b/pelican/tests/test_settings.py
index 8f12f3fd..708c0981 100644
--- a/pelican/tests/test_settings.py
+++ b/pelican/tests/test_settings.py
@@ -136,6 +136,8 @@ class TestSettingsConfiguration(unittest.TestCase):
             settings['ARTICLE_DIR']
             settings['PAGE_DIR']
 
+    # locale.getdefaultlocale() is broken on Windows
+    # See: https://bugs.python.org/issue37945
     @unittest.skipIf(platform == 'win32', "Doesn't work on Windows")
     def test_default_encoding(self):
         # Test that the default locale is set if not specified in settings
diff --git a/pelican/tests/test_utils.py b/pelican/tests/test_utils.py
index f0bc290d..e12c4378 100644
--- a/pelican/tests/test_utils.py
+++ b/pelican/tests/test_utils.py
@@ -757,35 +757,32 @@ class TestDateFormatter(unittest.TestCase):
 
 
 class TestSanitisedJoin(unittest.TestCase):
-    @unittest.skipIf(platform == 'win32',
-                     "Different filesystem root on Windows")
     def test_detect_parent_breakout(self):
         with self.assertRaisesRegex(
                 RuntimeError,
-                "Attempted to break out of output directory to /foo/test"):
+                "Attempted to break out of output directory to "
+                "(.*?:)?/foo/test"):  # (.*?:)? accounts for Windows root
             utils.sanitised_join(
                 "/foo/bar",
                 "../test"
             )
 
-    @unittest.skipIf(platform == 'win32',
-                     "Different filesystem root on Windows")
     def test_detect_root_breakout(self):
         with self.assertRaisesRegex(
                 RuntimeError,
-                "Attempted to break out of output directory to /test"):
+                "Attempted to break out of output directory to "
+                "(.*?:)?/test"):  # (.*?:)? accounts for Windows root
             utils.sanitised_join(
                 "/foo/bar",
                 "/test"
             )
 
-    @unittest.skipIf(platform == 'win32',
-                     "Different filesystem root on Windows")
     def test_pass_deep_subpaths(self):
         self.assertEqual(
             utils.sanitised_join(
                 "/foo/bar",
                 "test"
             ),
-            os.path.join("/foo/bar", "test")
+            utils.posixize_path(
+                os.path.abspath(os.path.join("/foo/bar", "test")))
         )
diff --git a/pelican/tools/pelican_import.py b/pelican/tools/pelican_import.py
index e288711e..b74da750 100755
--- a/pelican/tools/pelican_import.py
+++ b/pelican/tools/pelican_import.py
@@ -728,8 +728,9 @@ def download_attachments(output_path, urls):
 
         # Generate percent-encoded URL
         scheme, netloc, path, query, fragment = urlsplit(url)
-        path = quote(path)
-        url = urlunsplit((scheme, netloc, path, query, fragment))
+        if scheme != 'file':
+            path = quote(path)
+            url = urlunsplit((scheme, netloc, path, query, fragment))
 
         if not os.path.exists(full_path):
             os.makedirs(full_path)
diff --git a/pelican/utils.py b/pelican/utils.py
index 1f3d502c..64a308c1 100644
--- a/pelican/utils.py
+++ b/pelican/utils.py
@@ -27,8 +27,10 @@ logger = logging.getLogger(__name__)
 
 
 def sanitised_join(base_directory, *parts):
-    joined = os.path.abspath(os.path.join(base_directory, *parts))
-    if not joined.startswith(os.path.abspath(base_directory)):
+    joined = posixize_path(
+        os.path.abspath(os.path.join(base_directory, *parts)))
+    base = posixize_path(os.path.abspath(base_directory))
+    if not joined.startswith(base):
         raise RuntimeError(
             "Attempted to break out of output directory to {}".format(
                 joined
@@ -391,10 +393,9 @@ def get_relative_path(path):
 
 def path_to_url(path):
     """Return the URL corresponding to a given path."""
-    if os.sep == '/':
-        return path
-    else:
-        return '/'.join(split_all(path))
+    if path is not None:
+        path = posixize_path(path)
+    return path
 
 
 def posixize_path(rel_path):
diff --git a/pelican/writers.py b/pelican/writers.py
index 7b14714a..9b27a748 100644
--- a/pelican/writers.py
+++ b/pelican/writers.py
@@ -1,5 +1,6 @@
 import logging
 import os
+from posixpath import join as posix_join
 from urllib.parse import urljoin
 
 from feedgenerator import Atom1Feed, Rss201rev2Feed, get_tag_uri
@@ -25,7 +26,7 @@ class Writer:
 
         # See Content._link_replacer for details
         if self.settings['RELATIVE_URLS']:
-            self.urljoiner = os.path.join
+            self.urljoiner = posix_join
         else:
             self.urljoiner = lambda base, url: urljoin(
                 base if base.endswith('/') else base + '/', url)
diff --git a/requirements/docs.pip b/requirements/docs.pip
index acc5d5f5..bd25c939 100644
--- a/requirements/docs.pip
+++ b/requirements/docs.pip
@@ -1,3 +1,3 @@
-sphinx==1.4.9
+sphinx
 sphinx_rtd_theme
 livereload
diff --git a/requirements/test.pip b/requirements/test.pip
index 81d74c4e..973b27ca 100644
--- a/requirements/test.pip
+++ b/requirements/test.pip
@@ -1,6 +1,5 @@
 # Tests
 Pygments==2.6.1
-mock
 pytest==5.3.5
 pytest-cov
 pytest-xdist
diff --git a/tasks.py b/tasks.py
index 495194ab..52bfe6a3 100644
--- a/tasks.py
+++ b/tasks.py
@@ -24,7 +24,7 @@ PRECOMMIT = (
 @task
 def docbuild(c):
     """Build documentation"""
-    c.run(f"{VENV_BIN}/sphinx-build docs docs/_build")
+    c.run(f"{VENV_BIN}/sphinx-build -W docs docs/_build")
 
 
 @task(docbuild)
diff --git a/tox.ini b/tox.ini
index 23bb518f..18b0e7a4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,11 +1,12 @@
 [tox]
-envlist = py{35,36,37},docs,flake8
+envlist = py{3.5,3.6,3.7,3.8},docs,flake8
 
 [testenv]
 basepython =
-    py35: python3.5
-    py36: python3.6
-    py37: python3.7
+    py3.5: python3.5
+    py3.6: python3.6
+    py3.7: python3.7
+    py3.8: python3.8
 passenv = *
 usedevelop=True
 deps =
@@ -13,7 +14,7 @@ deps =
 
 commands =
     {envpython} --version
-    pytest -sv --cov=pelican pelican
+    pytest -s --cov=pelican pelican
 
 [testenv:docs]
 basepython = python3.6
@@ -27,7 +28,7 @@ commands =
 filterwarnings =
     default::DeprecationWarning
     error:.*:Warning:pelican
-addopts = -n 2
+addopts = -n 2 -r a
 
 [flake8]
 application-import-names = pelican