Merge pull request mohankishore#260 from mohankishore/pyup-update-flake8-3.6.0-to-3.7.7

Update flake8 to 3.7.7

Author: mohankishore

requirements_dev.txt

@@ -2,13 +2,10 @@ pip==19.1.1
 bumpversion==0.5.3
 wheel==0.33.4
 watchdog==0.9.0
-flake8==3.6.0
+flake8==3.7.7
 tox==3.9.0
 coverage==4.5.1
 Sphinx==1.8.1
 twine==1.13.0
 sphinx_rtd_theme==0.4.3
 pytest==4.5.0
-twine==1.13.0
-sphinx_rtd_theme==0.4.2
-pytest==4.5.0