check more pythons

Author: orsinium

.travis.yml

@@ -28,8 +28,17 @@ script:
 matrix:
   include:
 
+    - python: "3.5"
+      env: ENV=pytest
+
+    - python: "3.6.7"
+      env: ENV=pytest
+
     - python: "3.7"
       env: ENV=pytest
 
+    - python: "3.8-dev"
+      env: ENV=pytest
+
     - python: "3.7"
       env: ENV=flake8