File "/home/anon/Electrum-3.3.6/electrum/gui/qt/main_window.py", line 2854, in on_fee_type
  File "/home/anon/Electrum-3.3.6/electrum/simple_config.py", line 154, in set_key
  File "/home/anon/Electrum-3.3.6/electrum/simple_config.py", line 163, in _set_key_in_user_config
  File "/home/anon/Electrum-3.3.6/electrum/simple_config.py", line 243, in save_user_config