Bump flake8 from 3.7.7 to 3.7.8

Bumps [flake8](https://gitlab.com/pycqa/flake8) from 3.7.7 to 3.7.8.
- [Release notes](https://gitlab.com/pycqa/flake8/tags)
- [Commits](https://gitlab.com/pycqa/flake8/compare/3.7.7...3.7.8)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

setup.py

@@ -56,7 +56,7 @@ setup(
         'dev': [
             'nose==1.3.7',
             'coveralls==1.8.1',
-            'flake8==3.7.7',
+            'flake8==3.7.8',
             'xmlunittest==0.4.0'
         ]
     },