tox/travis: test py3.8 too

.travis.yml

@@ -23,6 +23,9 @@ matrix:
     - python: 3.7
       dist: xenial
       script: tox -e py37-coverage
+    - python: 3.8
+      dist: bionic
+      script: tox -e py38-coverage
     - python: nightly
       script: tox -e py-coverage
     - python: 3.6

tox.ini

@@ -4,8 +4,8 @@
 # and then run "tox" from this directory.
 
 [tox]
-# useful envs: py27-nodilate, py35, py36, py37, pypy, flake8
-envlist = {py27-nodilate,py35,py36,py37}
+# useful envs: py27-nodilate, py35, py36, py37, py38, pypy, flake8
+envlist = {py27-nodilate,py35,py36,py37,py38}
 skip_missing_interpreters = True
 minversion = 2.4.0