Merge pull request #5825 from benoit-pierre/fix_travis_py38_jobs

travis: fix Python 3.8 jobs

Author: pradyunsg

.travis.yml

@@ -57,8 +57,12 @@ jobs:
 
     - env: GROUP=1
       python: 3.8-dev
+      dist: xenial
+      sudo: required
     - env: GROUP=2
       python: 3.8-dev
+      dist: xenial
+      sudo: required
 
   # It's okay to fail on the in-development CPython version.
   fast_finish: true