Update Error Message to be more Explicit

[mitchspano]

The error message of "A serious error has been identified" is not quite sufficient to let users know what to do next. It sounds like some unexpected error crashed the action instead of letting them know that the action was performing what it was intended to do, but there was a finding of type "error".

We should probably update the error message to something like:

"A serious error has been identified with the structure of the code in the scope of the pull request. This will need to be corrected before this pull request can be merged. Please see the comments for more details."