Update pytest-django from 3.4.7 to 3.4.8 (#587)

Author: pyup-bot

requirements-development.txt

@@ -10,7 +10,7 @@ isort==4.3.9
 mock==2.0.0
 pytest==4.3.0
 pytest-cov==2.6.1
-pytest-django==3.4.7
+pytest-django==3.4.8
 pytest-factoryboy==2.0.2
 recommonmark==0.5.0
 Sphinx==1.8.4