Given a scriptsig (as hex), extract the signatures.
    Return list of signatures on success
    Return None on error

def parse_multisig_scriptsig( scriptsig_hex ):
    """
    Given a scriptsig (as hex), extract the signatures.
    Return list of signatures on success
    Return None on error
    """
    try:
        script_parts = btc_script_deserialize(scriptsig_hex)
    except:
        if os.environ.get("BLOCKSTACK_TEST") == "1":
            traceback.print_exc()

        return None

    # sanity check 
    return script_parts