Travis: upgrade tox to 3.7.0 (#695)

blueyed · web-flow · commit bb8359ff12fb · 2019-01-21T20:51:59.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -80,7 +80,7 @@ stages:
     if: tag IS present
 
 install:
-  - pip install tox==3.3.0
+  - pip install tox==3.7.0
 
 script:
   - tox
