The error from apache after a 504 page
[info] mod_wsgi (pid=): Python home /var/venv/mybox. [info] mod_wsgi (pid=): Initializing Python. ImportError: No mod
On Ubuntu, if you want to use python3, you will have to uninstall libapache2-mod-wsgi-py and install libapache2-mod-wsgi-py3 instead if you obtained your mod_wsgi from the repository.
libapache2-mod-wsgi-py
libapache2-mod-wsgi-py3