Merge pull request #525 from adamtheturtle/pyup-update-mypy-0.570-to-0.600

Update mypy to 0.600

Author: adamtheturtle

dev-requirements.txt

@@ -8,7 +8,7 @@ flake8-quotes==0.14.0  # Require single quotes
 freezegun==0.3.10  # Freeze time in tests
 hypothesis==3.56.8  # Generate test cases
 isort==4.3.4  # Lint imports
-mypy==0.570  # Type checking
+mypy==0.600  # Type checking
 pip_check_reqs==2.0.1
 pydocstyle==2.1.1  # Lint docstrings
 pyenchant==2.0.0  # Bindings for a spellchecking sytem