commandtest: Fix test28 error detection

As a part of c799d150 I've introduced a test case that
tests whether passing error object between processes works. The
test spawns a child which reports a system error, parent process
then reads the error and compares with expected output. Problem
with this approach is that error message contains stringified
errno which is not portable. FreeBSD has generally different
messages than Linux. Therefore, use g_strerror() to do the errno
to string translation for us.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

tests/commandtest.c

@@ -1272,6 +1272,7 @@ test28(const void *unused G_GNUC_UNUSED)
     /* Not strictly a virCommand test, but this is the easiest place
      * to test this lower-level interface. */
     virErrorPtr err;
+    g_autofree char *msg = g_strdup_printf("some error message: %s", g_strerror(ENODATA));
 
     if (virProcessRunInFork(test28Callback, NULL) != -1) {
         fprintf(stderr, "virProcessRunInFork did not fail\n");
@@ -1285,10 +1286,10 @@ test28(const void *unused G_GNUC_UNUSED)
 
     if (!(err->code == VIR_ERR_SYSTEM_ERROR &&
           err->domain == 0 &&
-          STREQ(err->message, "some error message: No data available") &&
+          STREQ(err->message, msg) &&
           err->level == VIR_ERR_ERROR &&
           STREQ(err->str1, "%s") &&
-          STREQ(err->str2, "some error message: No data available") &&
+          STREQ(err->str2, msg) &&
           err->int1 == ENODATA &&
           err->int2 == -1)) {
         fprintf(stderr, "Unexpected error object\n");