Fixed #1630, added test case for cookie persistence.

requests/sessions.py

@@ -146,6 +146,13 @@ class SessionRedirectMixin(object):
 
             extract_cookies_to_jar(self.cookies, prepared_request, resp.raw)
 
+            # Restore original cookies in redirects response.
+            headers = resp.request.headers
+            try:
+                headers['Cookie'] = req.headers['Cookie']
+            except KeyError:
+                pass
+
             i += 1
             yield resp
 

test_requests.py

@@ -164,6 +164,12 @@ class RequestsTestCase(unittest.TestCase):
         s.get(httpbin('cookies/set?foo="bar:baz"'))
         self.assertTrue(s.cookies['foo'] == '"bar:baz"')
 
+    def test_cookie_persists_via_api(self):
+        s = requests.session()
+        r = s.get(httpbin('redirect/1'), cookies={'foo':'bar'})
+        self.assertTrue('foo' in r.request.headers['Cookie'])
+        self.assertTrue('foo' in r.history[0].request.headers['Cookie'])
+
     def test_request_cookie_overrides_session_cookie(self):
         s = requests.session()
         s.cookies['foo'] = 'bar'