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

@@ -6,7 +6,7 @@
 EXTRAS_REQUIRE = {
     "django": DJANGO_REQUIRES,
     "tests": ["pytest"] + DJANGO_REQUIRES,
-    "lint": ["flake8==3.7.7", "flake8-bugbear==19.3.0", "pre-commit~=1.17"],
+    "lint": ["flake8==3.7.8", "flake8-bugbear==19.3.0", "pre-commit~=1.17"],
 }
 EXTRAS_REQUIRE["dev"] = EXTRAS_REQUIRE["tests"] + EXTRAS_REQUIRE["lint"] + ["tox"]
 PYTHON_REQUIRES = ">=3.5"