def expand_file_names(path, files_root):
    """
    Expands paths (e.g. css/*.css in files_root /actual/path/to/css/files/)
    """
    # For non-wildcards just return the path. This allows us to detect when
    # explicitly listed files are missing.
    if not any(wildcard in path for wildcard in '*?['):
        return [path]
    else:
        dir_path, filename = os.path.split(path)
        return [os.path.join(dir_path, f) for f in fnmatch.filter(os.listdir(os.path.join(files_root, dir_path)), filename)]