Creates an VSGSuite instance from a filename.

        :param str filename:  The fully qualified path to the VSG configuration file.

def from_file(cls, filename):
        """
        Creates an VSGSuite instance from a filename.

        :param str filename:  The fully qualified path to the VSG configuration file.
        """
        # Read the configuration file
        config = VSGConfigParser()
        if filename not in config.read([filename]):
            raise ValueError('Could not read VSG configuration file %s.' % filename)

        # set the root
        root = config.get('vsgen', 'root')
        root = os.path.normpath(os.path.join(os.path.dirname(filename), root))
        config.set('vsgen', 'root', root)

        return VSGSuite(config)