Update sessions.py

-Made removing a key-value pair more modular
-Remove unneeeded return statement

requests/sessions.py

@@ -201,10 +201,7 @@ class SessionRedirectMixin(object):
                 prepared_request.body = None
 
             headers = prepared_request.headers
-            try:
-                del headers['Cookie']
-            except KeyError:
-                pass
+            headers.pop('Cookie', None)
 
             # Extract any cookies sent on the response to the cookiejar
             # in the new request. Because we've mutated our copied prepared
@@ -271,7 +268,6 @@ class SessionRedirectMixin(object):
         if new_auth is not None:
             prepared_request.prepare_auth(new_auth)
 
-        return
 
     def rebuild_proxies(self, prepared_request, proxies):
         """This method re-evaluates the proxy configuration by considering the