File "/home/user/.local/lib/python3.7/site-packages/electrum/gui/qt/main_window.py", line 3256, in closeEvent
  File "/home/user/.local/lib/python3.7/site-packages/electrum/gui/qt/main_window.py", line 3265, in clean_up
  File "/home/user/.local/lib/python3.7/site-packages/electrum/simple_config.py", line 154, in set_key
  File "/home/user/.local/lib/python3.7/site-packages/electrum/simple_config.py", line 163, in _set_key_in_user_config
  File "/home/user/.local/lib/python3.7/site-packages/electrum/simple_config.py", line 243, in save_user_config