Log errno description upon QWK pack mutex file creation failure

src/sbbs3/ftpsrvr.c

@@ -4189,8 +4189,8 @@ static void ctrl_thread(void* arg)
 					lprintf(LOG_INFO,"%04d <%s> creating QWK packet...",sock,user.alias);
 					sprintf(str,"%spack%04u.now",scfg.data_dir,user.number);
 					if(!fmutex(str, startup->host_name, /* max_age: */60 * 60)) {
-						lprintf(LOG_WARNING, "%04d <%s> !ERROR %d creating mutex-semaphore file: %s"
-							,sock, user.alias, errno, str);
+						lprintf(LOG_WARNING, "%04d <%s> !ERROR %d (%s) creating mutex-semaphore file: %s"
+							,sock, user.alias, errno, strerror(errno), str);
 						sockprintf(sock,sess,"451 Packet creation already in progress (are you logged-in concurrently?)");
 						filepos=0;
 						continue;