fix contextlib.closing bug for sessions where content is not consumed…

… (issue psf#2593)

AUTHORS.rst

@@ -158,3 +158,4 @@ Patches and Suggestions
 - Ulrich Petri (`@ulope <https://github.com/ulope>`_)
 - Muhammad Yasoob Ullah Khalid <yasoob.khld@gmail.com> (`@yasoob <https://github.com/yasoob>`_)
 - Paul van der Linden (`@pvanderlinden <https://github.com/pvanderlinden>`_)
+- Colin Dickson (`@colindickson <https://github.com/colindickson>`_)

requests/models.py

@@ -842,4 +842,7 @@ def close(self):
 
         *Note: Should not normally need to be called explicitly.*
         """
+        if not self._content_consumed:
+            return self.raw.close()
+
         return self.raw.release_conn()

test_requests.py

@@ -9,6 +9,7 @@
 import pickle
 import unittest
 import collections
+import contextlib
 
 import io
 import requests
@@ -1060,6 +1061,15 @@ def test_response_iter_lines(self):
         next(it)
         assert len(list(it)) == 3
 
+    def test_unconsumed_session_response_closes_connection(self):
+        s = requests.session()
+
+        with contextlib.closing(s.get(httpbin('stream/4'), stream=True)) as response:
+            pass
+
+        self.assertEqual(response._content_consumed, False)
+        self.assertTrue(response.raw.closed, True)
+
     @pytest.mark.xfail
     def test_response_iter_lines_reentrant(self):
         """Response.iter_lines() is not reentrant safe"""