How to notify a user that the file is read-only

Today komodo (9.0.0) opens a read-only file without any notification. User can write his code for hours and only when try to save them gets a ‘can not write’ note.
Gvim, for example, echoes an warning message before editing the read-only file. Emacs does not allow edition at all.
How to add any kind of notification before user tries to edit a read-only file?
I talk about Linux RH6 system.

I see this feature was discussed years ago:

Please file an enhancement request on our bug tracker: