Improve Error handling for inactive user login

[will-moore]

See https://forum.image.sc/t/clearer-login-error-message-when-user-is-inactive/93936

When an Inactive user tries to login the message is not helpful...

Error: Connection not available, please check your user name and password.

Trying to trace this logic and error handling...

We first get SecurityViolation at https://github.com/ome/omero-py/blob/d76e17aa58ca755d239e9e8005712cd78239c62e/src/omero/gateway/__init__.py#L2185
because user is not in user group.

Then try to _createSession() again at https://github.com/ome/omero-py/blob/d76e17aa58ca755d239e9e8005712cd78239c62e/src/omero/gateway/__init__.py#L2203
but this time we don't get a SecurityViolation - instead we get

omero.ClientError Session already active. Create a new omero.client or closeSession()

but this isn't caught anywhere in the BlitzGateway - it is instead caught and ignored at

omero-web/omeroweb/connector.py

Line 180 in bb3ae5c

except Exception:

So the code that calls that at

omero-web/omeroweb/webgateway/views.py

Line 3424 in bb3ae5c

conn = connector.create_connection(

doesn't know why the connection failed. It then generates the misleading error message above.

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/clearer-login-error-message-when-user-is-inactive/93936/2