def require(repository_ctx, executable):
    path = repository_ctx.which(executable)
    if path == None:
        fail("{} must be available in PATH.".format(executable))
    return path


def execute(repository_ctx, arguments):
    result = repository_ctx.execute(arguments)
    if result.return_code != 0:
        fail("command failed: {}\n{}".format(" ".join(arguments), result.stderr))
    return result.stdout.strip()