Package congress-server is missing python-antlr3 dependency

Installed and configured (with puppet-congress) OpenStack Congress version Ocata on Xenial with UCA. Starting it resulted in the following error:

# congress-server --config-file=/etc/congress/congress.conf --log-file=/var/log/congress/congress-server.log
Traceback (most recent call last):
  File "/usr/bin/congress-server", line 6, in <module>
    from congress.server.congress_server import main
  File "/usr/lib/python2.7/dist-packages/congress/server/congress_server.py", line 40, in <module>
    from congress.common import eventlet_server
  File "/usr/lib/python2.7/dist-packages/congress/common/eventlet_server.py", line 38, in <module>
    from congress.dse2 import dse_node
  File "/usr/lib/python2.7/dist-packages/congress/dse2/dse_node.py", line 32, in <module>
    from congress.datalog import compile as datalog_compile
  File "/usr/lib/python2.7/dist-packages/congress/datalog/compile.py", line 38, in <module>
    from congress.datalog import CongressLexer
  File "/usr/lib/python2.7/dist-packages/congress/datalog/CongressLexer.py", line 4, in <module>
    from antlr3 import *
ImportError: No module named antlr3

Resolved this error by installing python-antlr3, so it seems this should be a hard package dependency.