require pytest-cov

Author: pgajdos

.travis.yml

@@ -6,7 +6,7 @@ python:
 sudo: false
 install:
     - pip install -U pip
-    - pip install -U --upgrade-strategy eager ".[test]" coveralls
+    - pip install -U --upgrade-strategy eager ".[test]" coveralls pytest-cov
     - pip freeze
 script:
     - pytest --cov=traittypes traittypes