Merge branch 'dep-update'

* dep-update:
  Update mypy package to 0.941
  Update flake8 package to 4.0.1
  Update coverage package to 6.3.2

requirements-test.txt

@@ -1,4 +1,4 @@
 # Testing
-coverage==5.5                    # Test coverage
-flake8==3.9.2                    # Python linting
-mypy==0.910                      # Static typing
+coverage==6.3.2                  # Test coverage
+flake8==4.0.1                    # Python linting
+mypy==0.941                      # Static typing