File "electrum/gui/qt/main_window.py", line 3018, in closeEvent
  File "electrum/gui/qt/main_window.py", line 3024, in clean_up
  File "electrum/simple_config.py", line 160, in set_key
  File "electrum/simple_config.py", line 169, in _set_key_in_user_config
  File "electrum/simple_config.py", line 261, in save_user_config