Be specific about which "illegal character" we just saw in the cert.

svn:r3699

src/common/tortls.c

@@ -625,7 +625,8 @@ tor_tls_get_peer_cert_nickname(tor_tls *tls, char *buf, size_t buflen)
   if (lenout == -1)
     goto error;
   if (((int)strspn(buf, LEGAL_NICKNAME_CHARACTERS)) < lenout) {
-    log_fn(LOG_WARN, "Peer certificate nickname has illegal characters.");
+    log_fn(LOG_WARN, "Peer certificate nickname '%s' has illegal characters.",
+           buf);
     goto error;
   }
   X509_free(cert);