Update pylint from 1.8.3 to 1.8.4

Author: pyup-bot

dev-requirements.txt

@@ -12,7 +12,7 @@ mypy==0.570  # Type checking
 pip_check_reqs==2.0.1
 pydocstyle==2.1.1  # Lint docstrings
 pyenchant==2.0.0  # Bindings for a spellchecking sytem
-pylint==1.8.3  # Lint
+pylint==1.8.4  # Lint
 pyroma==2.3  # Packaging best practices checker
 pytest-cov==2.5.1  # Measure code coverage
 pytest-envfiles==0.1.0  # Use files for environment variables for tests