File "electrum/gui/qt/main_window.py", line 3160, in closeEvent
  File "electrum/gui/qt/main_window.py", line 3169, in clean_up
  File "electrum/simple_config.py", line 149, in set_key
  File "electrum/simple_config.py", line 158, in _set_key_in_user_config
  File "electrum/simple_config.py", line 240, in save_user_config