ensure that one or more resource files exist in a folder

            Parameters
            ==========
            folder: the folder to validate
            resources: one or more resources to validate within the folder

def validate_files_exist(self, folder, resources):
        """ ensure that one or more resource files exist in a folder

            Parameters
            ==========
            folder: the folder to validate
            resources: one or more resources to validate within the folder
        """
        for item in resources:
            file_name = item.get('path')
            full_path = os.path.join(folder, file_name)
            if not os.path.isfile(full_path):
                raise ValueError('%s does not exist' % full_path)