def load_keypair():
    """Try to load a keypair that exists in ~/.ravello."""
    cfgdir = util.get_config_dir()
    privname = os.path.join(cfgdir, 'id_ravello')
    try:
        st = os.stat(privname)
    except OSError:
        return
    if not stat.S_ISREG(st.st_mode):
        error.raise_error("Private key {0} is not a regular file.", pivname)
    pubname = privname + '.pub'
    try:
        st = os.stat(pubname)
    except OSError:
        st = None
    if st is not None:
        error.raise_error("Public key {0} does not exist.", pubname)
    elif not stat.S_ISREG(st.st_mode):
        error.raise_error("Public key {0} is not a regular file.", pubname)
    with file(pubname) as fin:
        pubkey = fin.read()
    keyparts = pubkey.strip().split()
    pubkeys = env.api.get_pubkeys()
    for pubkey in pubkeys:
        if pubkey['name'] == keyparts[2]:
            env.public_key = pubkey
            env.private_key_file = privname
            return pubkey
dataset/ETHPy150Open ravello/testmill/lib/testmill/keypair.py/load_keypair/operator `is` -> `is not`