Feature Request: Add Error Message When Serial Connection Fails Due to Permissions on Linux

[Mississippi12]

I recently dealt with an issue connecting Luban to my SM 2.0 via serial (#2466). When I attempted to connect, the "connect" button would grey out, and a spinning wheel would appear in it. There would be no other indication that an error had occurred. However, the Luban log file does record an entry stating that access to the port was denied.

I suggest that an error message be added to the UI to notify the user of permissions issues.

(Note: I am uncertain, but this may only be an issue on linux based systems)