OSError: [Errno 28] No space left on device

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "electrum/gui/qt/settings_dialog.py", line 225, in <lambda>
  File "electrum/gui/qt/settings_dialog.py", line 219, in on_unit
  File "electrum/simple_config.py", line 694, in set_base_unit
  File "electrum/simple_config.py", line 170, in set_key
  File "electrum/simple_config.py", line 179, in _set_key_in_user_config
  File "electrum/simple_config.py", line 272, in save_user_config
OSError: [Errno 28] No space left on device