Reverted 6a64822b.

This commit caused every test that does two or more assertContains to
fail, because of #6527. It also made HttpResponse non-pickleable.

Refs #13222.

django/http/response.py

@@ -260,9 +260,9 @@ class HttpResponse(HttpResponseBase):
         else:
             self._container = [value]
             self._base_content_is_iter = False
-        self._iterator = iter(self._container)
 
     def __iter__(self):
+        self._iterator = iter(self._container)
         return self
 
     def __next__(self):
@@ -284,7 +284,7 @@ class HttpResponse(HttpResponseBase):
     def tell(self):
         if self._base_content_is_iter:
             raise Exception("This %s instance cannot tell its position" % self.__class__.__name__)
-        return len(self.content)
+        return sum([len(chunk) for chunk in self])
 
 
 class StreamingHttpResponse(HttpResponseBase):

tests/regressiontests/httpwrappers/tests.py

@@ -330,13 +330,6 @@ class HttpResponseTests(unittest.TestCase):
         self.assertRaises(UnicodeEncodeError,
                           getattr, r, 'content')
 
-    def test_iterator_isnt_rewound(self):
-        # Regression test for #13222
-        r = HttpResponse('abc')
-        i = iter(r)
-        self.assertEqual(list(i), [b'abc'])
-        self.assertEqual(list(i), [])
-
     def test_file_interface(self):
         r = HttpResponse()
         r.write(b"hello")