Transactions inherit writeConcern from client

Author: ShaneHarvey

pymongo/client_session.py

@@ -256,14 +256,18 @@ def _finish_transaction(self, command_name):
  self._server_session._transaction_id += 1
  return
 
+ write_concern = self._current_transaction_opts.write_concern
+ if write_concern is None:
+ write_concern = self.client.write_concern
+
  # TODO: retryable. And it's weird to pass parse_write_concern_error
  # from outside database.py.
  self._client.admin.command(
  command_name,
  txnNumber=self._server_session.transaction_id,
  stmtId=self._server_session.statement_id,
  session=self,
- write_concern=self._current_transaction_opts.write_concern,
+ write_concern=write_concern,
  read_preference=self._current_txn_read_pref,
  parse_write_concern_error=True)
  finally: