@Override
    public UserContext redecorate(UserContext decorated, UserContext context,
            AuthenticatedUser authenticatedUser,
            Credentials credentials) throws GuacamoleException {

        // Do nothing if underlying auth provider could not be loaded
        if (authProvider == null)
            return context;

        // Delegate to underlying auth provider
        return authProvider.redecorate(decorated, context,
                authenticatedUser, credentials);

    }
Logs a warning that the authentication process will be entirely aborted
due to an internal error, advising the administrator to set the
"skip-if-unavailable" property if error encountered is expected and
should be tolerated.
guacamole/src/main/java/org/apache/guacamole/extension/AuthenticationProviderFacade.java