jenkins.build.log() is rejected with jenkins: build.log: forbidden

I write a node.js app that interacts with jenkins and uses node-jenkins.

It works well with APIs like jenkins.job.get and jenkins.build.get, but when I try to use jenkins.build.logor jenkins.build.logStream, it fails with an error: jenkins: build.log: forbidden.

The returned message in the failure response is No valid crumb was included in the request.

What am I doing wrong?

(I opened an issue for this as well)

We use Jenkins version 2.7.1.

via splintor