When an UnauthorizedException is thrown by content service, the only message is:
User does not have access to 'read' 'content'
since the call is done with:
throw new UnauthorizedException( 'content', 'read' );

the message could be improved, passing extra information when throwing the exception, making use of the extra parameters accepted by
UnauthorizedException::__construct( $module, $function, array $properties = null, Exception $previous = null )