Try bionic, refs #71

.travis.yml

@@ -1,5 +1,5 @@
 language: python
-dist: xenial
+dist: bionic
 
 # 3.6 is listed first so it gets used for the later build stages
 python:
@@ -8,8 +8,6 @@ python:
   - "3.8-dev"
 
 script:
-  - sudo add-apt-repository ppa:jonathonf/backports -y
-  - sudo apt-get update && sudo apt-get install sqlite3
   - pip install -U pip wheel
   - pip install .[test]
   # Only run the numpy/pandas tests on Python 3.7: