Also there is nothing in the logs.
After I uncommented in httpd.conf the line
I've got more info about the issue.
It was permission error:
ValueError: Unable to configure handler 'file': [Errno 13] Permission denied: '/var/log/mailman-web/mailman-web.log'
After I corrected permissions for log file mentioned I can access Postorius and Hyperkitty. Everything looks working, I will test in more details later.