envelope_set_errormsg
envelope_set_errormsg(&evp, "%s", status);
envelope_set_errormsg(&evp, "Envelope expired");
envelope_set_errormsg(&evp, "%s", reason);
envelope_set_errormsg(&evp, "%s", reason);
envelope_set_errormsg(&evp, "%s", "Loop detected");
void envelope_set_errormsg(struct envelope *, char *, ...)