Better error message for unprivileged bootc usroverlay

[LukeShortCloud]

The error message for running bootc usroverlay as a non-root user does not make much sense.

$ bootc usroverlay
error: Read-only file system
$ sudo bootc usroverlay
Development mode enabled.  A writable overlayfs is now mounted on /usr.
All changes there will be discarded on reboot.

Perhaps it can suggest running as the root user instead.

There are also two spaces after the first sentence in the usroverlay message. I'm not sure if that's intentional or not.

[LukeShortCloud]

bootc image copy-to-storage has a better message. The important part is:

Querying root privilege: This command requires root privileges

[allisonkarlitskaya]

This is just a wrapper around the ostree admin unlock command and the error message comes from there. We could try to check in bootc if we're root before calling ostree, but this is probably better fixed in ostree itself.

[LukeShortCloud]

Thank you for the insight!

Should I move this GitHub Issue over to https://github.com/ostreedev/ostree then?