travis: use fullchain to verify ssl certificate

.travis.yml

@@ -26,6 +26,7 @@ script:
   - ./letsencrypt.sh --cron
   - ./letsencrypt.sh
   - openssl x509 -in "certs/${TMP_URL}/cert.pem" -noout -text
-  - openssl verify -verbose -CAfile "certs/lets-encrypt-staging.pem" -purpose sslserver "certs/${TMP_URL}/cert.pem"
+  - errout="$(openssl verify -verbose -CAfile "certs/${TMP_URL}/fullchain.pem" -purpose sslserver "certs/${TMP_URL}/fullchain.pem" | grep -v ': OK$')"
+  - if [[ ! -z "${errout}" ]]; then printf -- "${errout}"; exit 1; fi
   - rm private_key.pem
   - ./letsencrypt.sh --revoke "certs/${TMP_URL}/cert.pem" --privkey "certs/${TMP_URL}/privkey.pem"