daemon: Add early libvirtd start verbose errors.

Early errors during start of libvirtd didn't have
an error reporting mechanism and caused libvirtd
to exit silently (only the return value indicated
an error).

Libvirt logging is initialized very early using
enviroment variables and the internal error reporting
API is used to report early errors.

 v2 changes:
 - print errors unconditionaly before logging starts
 - fix message to US spelling
 v2.5 changes:
 - initialize logging from enviroment
 - log all early errors using VIR_ERROR
 v3 changes:
 - move virSetLogFromEnv() after virInitialize()

fixes: https://bugzilla.redhat.com/show_bug.cgi?id=728654

daemon/libvirtd.c

@@ -1270,6 +1270,9 @@ int main(int argc, char **argv) {
         exit(EXIT_FAILURE);
     }
 
+    /* initialize early logging */
+    virLogSetFromEnv();
+
     while (1) {
         int optidx = 0;
         int c;
@@ -1305,14 +1308,18 @@ int main(int argc, char **argv) {
 
         case 'p':
             VIR_FREE(pid_file);
-            if (!(pid_file = strdup(optarg)))
+            if (!(pid_file = strdup(optarg))) {
+                VIR_ERROR(_("Can't allocate memory"));
                 exit(EXIT_FAILURE);
+            }
             break;
 
         case 'f':
             VIR_FREE(remote_config_file);
-            if (!(remote_config_file = strdup(optarg)))
+            if (!(remote_config_file = strdup(optarg))) {
+                VIR_ERROR(_("Can't allocate memory"));
                 exit(EXIT_FAILURE);
+            }
             break;
 
         case OPT_VERSION:
@@ -1324,27 +1331,33 @@ int main(int argc, char **argv) {
             return 2;
 
         default:
-            fprintf (stderr, _("%s: internal error: unknown flag: %c\n"),
-                     argv[0], c);
+            VIR_ERROR(_("%s: internal error: unknown flag: %c"),
+                      argv[0], c);
             exit (EXIT_FAILURE);
         }
     }
 
-    if (!(config = daemonConfigNew(privileged)))
+    if (!(config = daemonConfigNew(privileged))) {
+        VIR_ERROR(_("Can't create initial configuration"));
         exit(EXIT_FAILURE);
+    }
 
     /* No explicit config, so try and find a default one */
     if (remote_config_file == NULL) {
         implicit_conf = true;
         if (daemonConfigFilePath(privileged,
-                                 &remote_config_file) < 0)
+                                 &remote_config_file) < 0) {
+            VIR_ERROR(_("Can't determine config path"));
             exit(EXIT_FAILURE);
+        }
     }
 
     /* Read the config file if it exists*/
     if (remote_config_file &&
-        daemonConfigLoad(config, remote_config_file, implicit_conf) < 0)
+        daemonConfigLoad(config, remote_config_file, implicit_conf) < 0) {
+        VIR_ERROR(_("Can't load config file '%s'"), remote_config_file);
         exit(EXIT_FAILURE);
+    }
 
     if (config->host_uuid &&
         virSetHostUUIDStr(config->host_uuid) < 0) {
@@ -1352,19 +1365,25 @@ int main(int argc, char **argv) {
         exit(EXIT_FAILURE);
     }
 
-    if (daemonSetupLogging(config, privileged, verbose, godaemon) < 0)
+    if (daemonSetupLogging(config, privileged, verbose, godaemon) < 0) {
+        VIR_ERROR(_("Can't initialize logging"));
         exit(EXIT_FAILURE);
+    }
 
     if (!pid_file &&
         daemonPidFilePath(privileged,
-                          &pid_file) < 0)
+                          &pid_file) < 0) {
+        VIR_ERROR(_("Can't determine pid file path."));
         exit(EXIT_FAILURE);
+    }
 
     if (daemonUnixSocketPaths(config,
                               privileged,
                               &sock_file,
-                              &sock_file_ro) < 0)
+                              &sock_file_ro) < 0) {
+        VIR_ERROR(_("Can't determine socket paths"));
         exit(EXIT_FAILURE);
+    }
 
     if (godaemon) {
         char ebuf[1024];