Weld sometimes logs error messages without stack traces, unless you enable DEBUG for the relevant category. (Sometimes even TRACE.) The stack traces are logged by methods in Weld like catchingDebug and catchingTrace, and they all seem to use the log message "Catching" together with message codes like PROBE-000000 or WELD-ENV-000000 (ie a 6 digit padded 0).
In our test config (and our development config, eg docker/rundev.sh), we should enable filtered DEBUG logging for org.jboss.weld, so that "Catching" or "-000000" messages will get through. (Filtering by either one should be okay.)
Note that DEBUG messages like these aren't visible on stdout (or in docker logs), only in the file server.log. EDIT: https://github.com/zanata/zanata-platform/pull/181
Also, we probably should have made a similar change for Docker Hub in https://github.com/zanata/zanata-docker-files/blob/master/zanata-server/conf/standalone.xml