Don't set all session cookies on response.cookies
diff --git a/requests/sessions.py b/requests/sessions.py
index f37d009d14..eb6b1eb616 100644
--- a/requests/sessions.py
+++ b/requests/sessions.py
@@ -160,8 +160,6 @@ def resolve_redirects(self, resp, req, stream=False, timeout=None,
             i += 1
             yield resp
 
-        resp.cookies = self.cookies.copy()
-
 
 class Session(SessionRedirectMixin):
     """A Requests session.

This prevents all the session cookies from being set in response.cookies. I believe the old behavior was a workaround due to how session cookies were being updated before #1290
After this, response.cookies will match up with the set-cookies header for the response.

As discussed here: https://botbot.me/freenode/python-requests/msg/2568299/
