File "/tmp/.mount_electrvQRJG6/usr/lib/python3.7/site-packages/electrum/gui/qt/settings_dialog.py", line 401, in on_exchange
    self.fx.set_exchange(exchange)
  File "/tmp/.mount_electrvQRJG6/usr/lib/python3.7/site-packages/electrum/exchange_rate.py", line 594, in set_exchange
    self.config.set_key('use_exchange', name, True)
  File "/tmp/.mount_electrvQRJG6/usr/lib/python3.7/site-packages/electrum/simple_config.py", line 160, in set_key
    self._set_key_in_user_config(key, value, save)
  File "/tmp/.mount_electrvQRJG6/usr/lib/python3.7/site-packages/electrum/simple_config.py", line 169, in _set_key_in_user_config
    self.save_user_config()
  File "/tmp/.mount_electrvQRJG6/usr/lib/python3.7/site-packages/electrum/simple_config.py", line 262, in save_user_config
    f.write(s)