Fix crash when session.cookies was not a RequestsCookieJar

diff --git a/requests/sessions.py b/requests/sessions.py
index 40e4d82ba8ef825baa6b27100467bdafad57911c..1d3c5551320d9e695ca2a541733239dae76b07bc 100644 (file)
--- a/requests/sessions.py
+++ b/requests/sessions.py
@@ -9,6 +9,7 @@ requests (cookies, auth, proxies).
 
 """
 import os
+from copy import copy
 from datetime import datetime
 
 from .compat import cookielib
@@ -285,8 +286,9 @@ class Session(SessionRedirectMixin):
             cookies = cookiejar_from_dict(cookies)
 
         # Merge with session cookies
-        merged_cookies = self.cookies.copy()
-        merged_cookies.update(cookies)
+        merged_cookies = copy(self.cookies)
+        for cookie in cookies:
+            merged_cookies.set_cookie(cookie)
         cookies = merged_cookies
 
         # Gather clues from the surrounding environment.