File "site-packages\electrum-3.1.0-py3.5.egg\electrum_gui\qt\main_window.py", line 2981, in closeEvent
  File "site-packages\electrum-3.1.0-py3.5.egg\electrum_gui\qt\main_window.py", line 2988, in clean_up
  File "site-packages\electrum-3.1.0-py3.5.egg\electrum\simple_config.py", line 140, in set_key
  File "site-packages\electrum-3.1.0-py3.5.egg\electrum\simple_config.py", line 149, in _set_key_in_user_config
  File "site-packages\electrum-3.1.0-py3.5.egg\electrum\simple_config.py", line 214, in save_user_config