<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def gpg_command(args, env=None):
 """Prepare common GPG command line arguments."""

    if env is None:
        env = os.environ
    cmd = get_gnupg_binary(neopg_binary=env.get('NEOPG_BINARY'))
    return [cmd] + args