def AddPathIfNotExists(env_dict, key, path, sep=os.pathsep):
    """This function will take 'key' out of the dictionary
    'env_dict', then add the path 'path' to that key if it is not
    already there.  This treats the value of env_dict[key] as if it
    has a similar format to the PATH variable...a list of paths
    separated by tokens.  The 'path' will get added to the list if it
    is not already there."""
    try:
        is_list = 1
        paths = env_dict[key]
        if not is_List(env_dict[key]):
            paths = paths.split(sep)
            is_list = 0
        if os.path.normcase(path) not in list(map(os.path.normcase, paths)):
            paths = [ path ] + paths
        if is_list:
            env_dict[key] = paths
        else:
            env_dict[key] = sep.join(paths)
    except KeyError:
        env_dict[key] = path