def prepare_str_to_sign(req_tgt, hdrs):
    """
    Concatenates Intersight headers in preparation to be signed

    :param req_tgt : http method plus endpoint
    :param hdrs: dict with header keys
    :return: concatenated header authorization string
    """
    ss = ""
    ss = ss + "(request-target): " + req_tgt + "\n"

    length = len(hdrs.items())

    i = 0
    for key, value in hdrs.items():
        ss = ss + key.lower() + ": " + value
        if i < length - 1:
            ss = ss + "\n"
        i += 1

    return ss