Fixed #16241 -- Ensured the WSGI iterable's close() is always called.

Thanks Graham Dumpleton for the report.

django/core/servers/basehttp.py

@@ -109,6 +109,17 @@ class ServerHandler(simple_server.ServerHandler, object):
         super(ServerHandler, self).error_output(environ, start_response)
         return ['\n'.join(traceback.format_exception(*sys.exc_info()))]
 
+    # Backport of http://hg.python.org/cpython/rev/d5af1b235dab. See #16241.
+    # This can be removed when support for Python <= 2.7.3 is deprecated.
+    def finish_response(self):
+        try:
+            if not self.result_is_file() or not self.sendfile():
+                for data in self.result:
+                    self.write(data)
+                self.finish_content()
+        finally:
+            self.close()
+
 
 class WSGIServer(simple_server.WSGIServer, object):
     """BaseHTTPServer that implements the Python WSGI protocol"""