File "/usr/local/lib/python3.5/dist-packages/electrum_gui/qt/main_window.py", line 3001, in closeEvent
    self.clean_up()
  File "/usr/local/lib/python3.5/dist-packages/electrum_gui/qt/main_window.py", line 3008, in clean_up
    self.config.set_key("is_maximized", self.isMaximized())
  File "/usr/local/lib/python3.5/dist-packages/electrum/simple_config.py", line 143, in set_key
    self._set_key_in_user_config(key, value, save)
  File "/usr/local/lib/python3.5/dist-packages/electrum/simple_config.py", line 152, in _set_key_in_user_config
    self.save_user_config()
  File "/usr/local/lib/python3.5/dist-packages/electrum/simple_config.py", line 218, in save_user_config
    with open(path, "w", encoding='utf-8') as f: