Travis: re-enable Python 3.8
The Werkzeug issue on 3.8 seems to have been fixed:
@@ -24,9 +24,9 @@ matrix:
- python: 3.7
env: {TOX_ENV: py37-test}
dist: xenial
- # - python: 3.8-dev
- # env: {TOX_ENV: py38-test}
- # dist: xenial
+ - python: 3.8-dev
+ env: {TOX_ENV: py38-test}
+ dist: xenial
# - python: pypy
# - env: {TOX_ENV: pypy-test}
- python: 3.6
