Update pytest from 4.6.3 to 5.0.0 (#671)

Author: pyup-bot

requirements-development.txt

@@ -7,7 +7,7 @@ factory-boy==2.12.0
 flake8==3.7.7
 flake8-isort==2.7.0
 isort==4.3.21
-pytest==4.6.3
+pytest==5.0.0
 pytest-cov==2.7.1
 pytest-django==3.5.1
 pytest-factoryboy==2.0.3