File "electrum/gui/qt/network_dialog.py", line 462, in set_server
  File "electrum/network.py", line 299, in run_from_another_thread
  File "concurrent/futures/_base.py", line 432, in result
  File "concurrent/futures/_base.py", line 384, in __get_result
  File "electrum/util.py", line 908, in wrapper
  File "electrum/network.py", line 594, in set_parameters
  File "electrum/simple_config.py", line 154, in set_key
  File "electrum/simple_config.py", line 163, in _set_key_in_user_config
  File "electrum/simple_config.py", line 244, in save_user_config