log reason for bad verifier assertion and increment statsd failure counter - issue2016

bin/verifier

@@ -104,9 +104,11 @@ function doVerification(req, resp, next) {
     else if (!r || !r.success) err = "no response returned from child process";
 
     if (err) {
+      statsd.increment("assertion_failure");
       resp.json({"status":"failure", reason: err});  //Could be 500 or 200 OK if invalid cert
       metrics.report('verify', {
         result: 'failure',
+        reason: err,
         rp: audience
       });
     } else {