Fix pypy environment in Travis CI

bbc2 · bbc2 · commit 8815885ee1b8 · 2020-12-05T14:46:06.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -33,6 +33,7 @@ script:
   - tox
 
 before_install:
+  - pip install --upgrade pip
   - pip install coveralls
 
 after_success:
