HTTP20Connection: Fix use of ENABLE_PUSH

Fixes #372

Author: jayvdb

hyper/http20/connection.py

@@ -403,7 +403,7 @@ def _connect_upgrade(self, sock):
         with self._conn as conn:
             conn.initiate_upgrade_connection()
             conn.update_settings(
-                {h2.settings.ENABLE_PUSH: int(self._enable_push)}
+                {h2.settings.SettingCodes.ENABLE_PUSH: int(self._enable_push)}
             )
         self._send_outstanding_data()
 
@@ -424,7 +424,7 @@ def _send_preamble(self):
         with self._conn as conn:
             conn.initiate_connection()
             conn.update_settings(
-                {h2.settings.ENABLE_PUSH: int(self._enable_push)}
+                {h2.settings.SettingCodes.ENABLE_PUSH: int(self._enable_push)}
             )
         self._send_outstanding_data()