File "electrum/gui/qt/main_window.py", line 3256, in closeEvent
  File "electrum/gui/qt/main_window.py", line 3265, in clean_up
  File "electrum/simple_config.py", line 154, in set_key
  File "electrum/simple_config.py", line 163, in _set_key_in_user_config
  File "electrum/simple_config.py", line 244, in save_user_config