Report errors as "just expired"

clients/report_tlscert

@@ -23,10 +23,13 @@ report0 = []
 
 with socket.create_connection((args.hostname, args.port)) as sock:
     context = ssl.create_default_context()
+    try:
         with context.wrap_socket(sock, server_hostname=args.hostname) as ssock:
             cert = ssock.getpeercert()
             not_after = ssl.cert_time_to_seconds(cert["notAfter"])
             delta = not_after - now
+    except ssl.SSLCertVerificationError:
+        delta = 0
     report0.append({ "measure": "tls_cert_ttl", "unit": "s", "value": delta })
 
 report = [