Update pytest from 4.1.1 to 4.2.0

Author: pyup-bot

dev-requirements.txt

@@ -18,7 +18,7 @@ Pygments==2.3.1
 pylint==2.2.2  # Lint
 pyroma==2.4  # Packaging best practices checker
 pytest-cov==2.6.1  # Measure code coverage
-pytest==4.1.1  # Test runners
+pytest==4.2.0  # Test runners
 PyYAML==3.13
 Sphinx==1.8.3
 sphinx-autodoc-typehints==1.6.0