Allow latest Python-Markdown to be installed

Pinning dependencies to specific versions creates conflicts when other
packages require more recent versions. We can do our part by allowing
for a wider range of dependency versions, specifying only the oldest
version that will still work. Meanwhile, we ensure that test
environments use a specific pinned dependency in order to match the
expected functional test output.

pyproject.toml

@@ -39,12 +39,12 @@ pygments = "^2.6"
 python-dateutil = "^2.8"
 pytz = "^2020.1"
 unidecode = "^1.1"
-markdown = {version = "~3.2.2", optional = true}
+markdown = {version = "^3.2", optional = true}
 
 [tool.poetry.dev-dependencies]
 BeautifulSoup4 = "^4.9"
 lxml = "^4.3"
-markdown = "~3.2.2"
+markdown = "~3.3.3"
 typogrify = "^2.0"
 sphinx = "^3.0"
 sphinx_rtd_theme = "^0.5"

requirements/test.pip

@@ -5,7 +5,7 @@ pytest-cov
 pytest-xdist[psutil]
 
 # Optional Packages
-Markdown >= 3.1
+Markdown==3.3.3
 BeautifulSoup4
 lxml
 typogrify