support/scripts/pkg-stats: fix the status reporting of CVEs

Since commit bd665d182c8131d2deafa39be0f3d89adb43643f
("support/scripts/pkg-stats: improve rendering of CVE information"),
we have better reporting of CVE related information, based on
pkg.status['cve']. However, this commit broke pkg-stats when the
--nvd-path option is not passed, and therefore no CVE information is
available.

This commit fixes that, by making use of the is_status_ok(),
is_status_error() and is_status_na() methods recently introduced.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

support/scripts/pkg-stats

@@ -880,18 +880,20 @@ def dump_html_pkg(f, pkg):
 
     # CVEs
     td_class = ["centered"]
-    if pkg.status['cve'][0] == "ok":
+    if pkg.is_status_ok("cve"):
         td_class.append("cve-ok")
-    elif pkg.status['cve'][0] == "error":
+    elif pkg.is_status_error("cve"):
         td_class.append("cve-nok")
     else:
         td_class.append("cve-unknown")
     f.write("  <td class=\"%s\">\n" % " ".join(td_class))
-    if pkg.status['cve'][0] == "error":
+    if pkg.is_status_error("cve"):
         for cve in pkg.cves:
             f.write("   <a href=\"https://security-tracker.debian.org/tracker/%s\">%s<br/>\n" % (cve, cve))
-    elif pkg.status['cve'][0] == "na":
+    elif pkg.is_status_na("cve"):
         f.write("    %s" % pkg.status['cve'][1])
+    else:
+        f.write("    N/A\n")
     f.write("  </td>\n")
 
     # CPE ID