Spotted on gallium in /srv/org/wikimedia/doc there is a bunch of directories such as:
$ find /srv/org/wikimedia/doc -maxdepth 3 -wholename '*wmf/*' -type d ./Flow/wmf/1.26wmf15 ./Flow/wmf/1.26wmf12 ./Flow/wmf/1.26wmf19 ./Flow/wmf/1.26wmf16 ./Flow/wmf/1.26wmf22 ./Flow/wmf/1.27.0-wmf.3 ./Flow/wmf/1.26wmf24 ./Flow/wmf/1.26wmf17 ./Flow/wmf/1.27.0-wmf.1 ./Flow/wmf/1.26wmf10 ./Flow/wmf/1.26wmf18 ./Flow/wmf/1.26wmf9 ./Flow/wmf/1.27.0-wmf.6 ./Flow/wmf/1.26wmf11 ./Flow/wmf/1.27.0-wmf.2 ./Flow/wmf/1.26wmf21 ./Flow/wmf/1.26wmf20 ./Flow/wmf/1.26wmf13 ./Flow/wmf/1.27.0-wmf.4 ./Flow/wmf/1.27.0-wmf.5 ./MobileFrontend/wmf/1.26wmf16 ./MobileFrontend/wmf/1.26wmf22 ./MobileFrontend/wmf/1.27.0-wmf.3 ./MobileFrontend/wmf/1.26wmf24 ./MobileFrontend/wmf/1.27.0-wmf.1 ./MobileFrontend/wmf/1.26wmf23 ./MobileFrontend/wmf/1.27.0-wmf.2 ./MobileFrontend/wmf/1.26wmf21 ./MobileFrontend/wmf/1.26wmf20 ./MobileFrontend/wmf/1.27.0-wmf.4 $
Most probably the job is lacking a proper branch: filter in Zuul configuration.