Update pytest-cov from 2.6.0 to 2.6.1 (#546)

Author: pyup-bot

requirements-development.txt

@@ -9,7 +9,7 @@ flake8-isort==2.6.0
 isort==4.3.4
 mock==2.0.0
 pytest==4.0.2
-pytest-cov==2.6.0
+pytest-cov==2.6.1
 pytest-django==3.4.5
 pytest-factoryboy==2.0.2
 recommonmark==0.4.0