Travis CI: Test on Python 3.9

Author: cclauss

.travis.yml

@@ -1,21 +1,19 @@
-dist: xenial
+os: linux
+dist: focal
 language: python
 
-sudo: false
-
-matrix:
+jobs:
   include:
     - python: "3.7"
       env: TOXENV=py37
-    - python: "3.8"
-      env: TOXENV=py38
+    - python: "3.9"
+      env: TOXENV=py39
 
 cache:
   - pip
 
 install:
-  - pip install tox
-  - pip install codecov
+  - pip install codecov tox
 
 script:
   - tox