Thanks for reporting! This might be related to some recent changes that got deployed last week. I'll double check the error logs for details later today.

Found one error related to that PR:

16:29:25.344 ERROR bot: Error while triggering Jenkins build (req_id=56e73180-18da-11e9-8fbf-8bd7847363eb, pr=nodejs/node/#25516, action=/old?u=https%3A%2F%2Fgithub.com%2Fnodejs%2Fgithub-bot%2Fissues%2Fpull_request.opened%29&y=1999
    TypeError: The header content contains invalid characters
        at ClientRequest.OutgoingMessage.setHeader (_http_outgoing.js:359:11)
        at new ClientRequest (_http_client.js:85:14)
        at Object.exports.request (http.js:31:10)
        at Object.exports.request (https.js:206:15)
        at Object.request (/home/iojs/github-bot/node_modules/agent-base/patch-core.js:23:20)
        at Request.start (/home/iojs/github-bot/node_modules/request/request.js:751:32)
        at Request.write (/home/iojs/github-bot/node_modules/request/request.js:1497:10)
        at end (/home/iojs/github-bot/node_modules/request/request.js:549:18)
        at Immediate.<anonymous> (/home/iojs/github-bot/node_modules/request/request.js:578:7)
        at runCallback (timers.js:672:20)

There's lots of other successful Jenkins -> GitHub updates before and after the above, so I'm assuming it's related to the PR somehow.

Other recent failures (not exhaustive):
nodejs/node#25517 (comment)
nodejs/node#25510 (comment)
nodejs/node#25508 (comment)
nodejs/node#25507 (comment)
nodejs/node#25472 (comment)
nodejs/node#25461 (comment)
nodejs/node#25457 (comment)

Much appreciated! Grepping through logs from previous days, I also started realising this wasn't a unique error.. What's common between the ones I've seen, is they're related to webhook events from opened PRs.

Maybe related to #209? 🤷‍♂️

Similar errors from other days;

04:39:22.330 ERROR bot: Error while triggering Jenkins build (req_id=a6332ad0-161b-11e9-8fbf-8bd7847363eb, pr=nodejs/node/#25461, action=/old?u=https%3A%2F%2Fgithub.com%2Fnodejs%2Fgithub-bot%2Fissues%2Fpull_request.opened%29&y=1999
    TypeError: The header content contains invalid characters
        at ClientRequest.OutgoingMessage.setHeader (_http_outgoing.js:359:11)
--
18:32:29.524 ERROR bot: Error while triggering Jenkins build (req_id=08f61f00-1690-11e9-8fbf-8bd7847363eb, pr=nodejs/node/#25463, action=/old?u=https%3A%2F%2Fgithub.com%2Fnodejs%2Fgithub-bot%2Fissues%2Fpull_request.opened%29&y=1999
    TypeError: The header content contains invalid characters
        at ClientRequest.OutgoingMessage.setHeader (_http_outgoing.js:359:11)
--
21:00:38.068 ERROR bot: Error while triggering Jenkins build (req_id=baf86780-16a4-11e9-8fbf-8bd7847363eb, pr=nodejs/node/#25466, action=/old?u=https%3A%2F%2Fgithub.com%2Fnodejs%2Fgithub-bot%2Fissues%2Fpull_request.opened%29&y=1999
    TypeError: The header content contains invalid characters
        at ClientRequest.OutgoingMessage.setHeader (_http_outgoing.js:359:11)

Alrighty, #209 is now live in production. I'll remember to double check for these errors logs the next day.

This looks promising:

19:42:45.235  INFO bot: Jenkins build started (req_id=58a89c50-18f5-11e9-a5d5-f9690fa1f072, pr=nodejs/node/#25523, action=/old?u=https%3A%2F%2Fgithub.com%2Fnodejs%2Fgithub-bot%2Fissues%2Fpull_request.opened%29&y=1999
    buildUrl: https://ci.nodejs.org/blue/organizations/jenkins/node-test-pull-request-lite-pipeline/detail/node-test-pull-request-lite-pipeline/2257/pipeline

Closing this issue for now, feel free to re-open if I'm wrong :)

Refs nodejs/node#25523