Normally validation method is writen in each validation of parameters.
        But `include` of global section needs to be read before validation.

        :param str path: absolute path
        :rtype: bool
        :return: If given path passes validation, returns True.

def _validate_global_include(self, path):
        """
        Normally validation method is writen in each validation of parameters.
        But `include` of global section needs to be read before validation.

        :param str path: absolute path
        :rtype: bool
        :return: If given path passes validation, returns True.
        """
        if not path.endswith('/'):
            path = os.path.dirname(path)

        if os.path.exists(path):
            if not os.access(path, os.R_OK):
                raise blackbird.utils.error.BlackbirdError(
                    message=(
                        '{0}: Permission denied.'
                        ''.format(path)
                    )
                )

        else:
            raise blackbird.utils.error.BlackbirdError(
                message=(
                    '{0}: No such file or directory.'
                    ''.format(path)
                )
            )

        return True