'Returns the hexdigest string of the HMAC-SHA1 (RFC 2104) for
the information given.
:param request_method: HTTP method of the request.
:param path: The path to the resource.
:param x_timestamp: The X-Timestamp header value for the request.
:param nonce: A unique value for the request.
:param realm_key: Shared secret at the cluster operator level.
:param user_key: Shared secret at the user\'s container level.
:returns: hexdigest str of the HMAC-SHA1 for the request.'

def get_sig(self, request_method, path, x_timestamp, nonce, realm_key, user_key):

    nonce = get_valid_utf8_str(nonce)
    realm_key = get_valid_utf8_str(realm_key)
    user_key = get_valid_utf8_str(user_key)
    return hmac.new(realm_key, ('%s\n%s\n%s\n%s\n%s' % (request_method, path, x_timestamp, nonce, user_key)), hashlib.sha1).hexdigest()
