It turns out openqa does not like inline comments in its ini files

templates/etc/openqa/workers.ini.j2

@@ -1,9 +1,7 @@
 [global]
 HOST = https://{{ openqa_host }}
-CACHEDIRECTORY = /var/lib/openqa/cache  # desired cache location
-CACHELIMIT = 50                         # max. cache size in GiB, defaults to 50
-CACHE_MIN_FREE_PERCENTAGE = 10          # min. free disk space to preserve in percent
-CACHEWORKERS = 5                        # number of parallel cache minion workers, defaults to 5
+CACHEDIRECTORY = /var/lib/openqa/cache
+CACHE_MIN_FREE_PERCENTAGE = 10
 
 [https://{{ openqa_host }}]
-TESTPOOLSERVER = rsync://{{ openqa_host }}/tests # also cache tests (via rsync)
+TESTPOOLSERVER = rsync://{{ openqa_host }}/tests