ci: Travis: bump tox==3.9.0 (#797)

blueyed · web-flow · commit 8a5aa0b0cb3c · 2020-01-07T01:42:37.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -94,7 +94,7 @@ stages:
     if: tag IS present
 
 install:
-  - pip install tox==3.7.0
+  - pip install tox==3.9.0
 
 script:
   - tox
