nodeinfotest: Print error if cpuinfo file can't be opened

Currently, we are opening the cpuinfo file via fopen() which if fails
doesn't print any error message. We should do that instead.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

tests/nodeinfotest.c

@@ -39,8 +39,11 @@ linuxTestCompareFiles(const char *cpuinfofile,
         goto fail;
 
     cpuinfo = fopen(cpuinfofile, "r");
-    if (!cpuinfo)
+    if (!cpuinfo) {
+        fprintf(stderr, "unable to open: %s : %s\n",
+                cpuinfofile, strerror(errno));
         goto fail;
+    }
 
     memset(&nodeinfo, 0, sizeof(nodeinfo));
     if (linuxNodeInfoCPUPopulate(cpuinfo, sysfs_dir, arch, &nodeinfo) < 0) {