Fix python 3.7 -> 3.7-dev and add flake8 testing

Also fixed flake8 errors.

testproj/manage.py

@@ -11,7 +11,7 @@ if __name__ == "__main__":
         # issue is really that Django is missing to avoid masking other
         # exceptions on Python 2.
         try:
-            import django
+            import django  # noqa: F401
         except ImportError:
             raise ImportError(
                 "Couldn't import Django. Are you sure it's installed and "

testproj/snippets/admin.py

@@ -1,3 +1 @@
-from django.contrib import admin
-
 # Register your models here.

testproj/snippets/serializers.py

@@ -1,6 +1,5 @@
-from rest_framework.status import HTTP_400_BAD_REQUEST
-
 from rest_framework import serializers
+
 from snippets.models import Snippet, LANGUAGE_CHOICES, STYLE_CHOICES
 
 

testproj/testproj/runner.py

@@ -1,9 +1,10 @@
 import os
 
+
 class PytestTestRunner(object):
     """Runs pytest to discover and run tests."""
 
-    def __init__(self, verbosity=1, failfast=False, keepdb=False, **kwargs):
+    def __init__(self, verbosity=1, failfast=False, keepdb=False, **_):
         self.verbosity = verbosity
         self.failfast = failfast
         self.keepdb = keepdb

testproj/testproj/settings.py

@@ -1,7 +1,5 @@
 import os
 
-import sys
-
 # Build paths inside the project like this: os.path.join(BASE_DIR, ...)
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 

testproj/testproj/urls.py

@@ -25,5 +25,5 @@ urlpatterns = [
     url(r'^redoc/$', schema_view.with_ui('redoc', cache_timeout=None), name='schema-redoc'),
 
     url(r'^admin/', admin.site.urls),
-    url(f'^snippets/', include('snippets.urls')),
+    url(r'^snippets/', include('snippets.urls')),
 ]