Update pytest from 4.0.2 to 4.1.0 (#545)

Author: pyup-bot

requirements-development.txt

@@ -8,7 +8,7 @@ flake8==3.6.0
 flake8-isort==2.6.0
 isort==4.3.4
 mock==2.0.0
-pytest==4.0.2
+pytest==4.1.0
 pytest-cov==2.6.1
 pytest-django==3.4.5
 pytest-factoryboy==2.0.2