Fix pyflakes and pep8 errors

Use extra asserts to use previously unused variables in tests,
such as `cass` and `response`.

Fix only pyflakes errors in docs/conf.py

vcr/stubs/requests_stubs.py

@@ -10,8 +10,10 @@ from ..stubs import VCRHTTPConnection, VCRHTTPSConnection
 # urllib3 defines its own HTTPConnection classes, which requests goes ahead and assumes
 # you're using.  It includes some polyfills for newer features missing in older pythons.
 
+
 class VCRRequestsHTTPConnection(VCRHTTPConnection, HTTPConnection):
     _baseclass = HTTPConnection
 
+
 class VCRRequestsHTTPSConnection(VCRHTTPSConnection, VerifiedHTTPSConnection):
     _baseclass = VerifiedHTTPSConnection