Update pylint from 2.3.0 to 2.3.1

Author: pyup-bot

dev-requirements.txt

@@ -14,7 +14,7 @@ pydocstyle==3.0.0  # Lint docstrings
 pyenchant==2.0.0  # Bindings for a spellchecking sytem
 pygithub==1.43.5
 Pygments==2.3.1
-pylint==2.3.0  # Lint
+pylint==2.3.1  # Lint
 pyroma==2.4  # Packaging best practices checker
 pytest-cov==2.6.1  # Measure code coverage
 pytest==4.3.0  # Test runners