Test on Python 3.8 final
diff --git a/.travis.yml b/.travis.yml
index b95e479a21..91e60a7da9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,7 +17,7 @@ jobs:
     - stage: test
       python: '3.7'
     - stage: test
-      python: '3.8-dev'
+      python: '3.8'
     - stage: coverage
       python: '3.6'
       script: codecov

The Trove classifier is already added:
 
https://github.com/psf/requests/blob/fab1fd10d0b115e635b9ef1364f8444089725000/setup.py#L98
