@classmethod
def check_args(cls, config, options, args, parser, package_file=None):
    """
        Override in subclass if required.
        """
    if not args:
        parser.error('no input files specified')
    if not (package_file or options.package_file):
        parser.error('no package file specified')
    if not options.entry_point_process:
        parser.error('no entry point process specified')
