Probably since https://gerrit.wikimedia.org/r/#/c/59797/ job handling starts an external php process by default.
This fails if open_basedir does not contain /usr/bin/
There should be a check for the open_basedir, and an automatic fallback to the internal job queue.
Version: 1.22.1
Severity: major
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=58719
https://bugzilla.wikimedia.org/show_bug.cgi?id=62092