when config file is not writable, display a warning message
|Reported by:||matt||Owned by:|
When the config file is not writable, and the config file is written to disk, it currently silently fails. All writes to the config file are done on _destruct which means we can't display an error message to the screen when it fails.
Instead, on the screens that require a writable config file, we should display a warning message that the config file is not writable.
The screens affected are:
- Plugins management: plugin enable/disable
- Super user password reset
- Super user email change