wsgi.py: Fix broken error ouput for django.setup() call.
wsgi.py: Fix broken error ouput for django.setup() call.

It's common for a broken settings.py file to result in Django not
starting, thus never writing to `/var/log/zulip/errors.log`.  Such
behavior can be discouraging when the server 500s without a traceback
to accompany it.  To fix this, we simply catch any exceptions in
django.setup(), if raised, and log the exception appropriately.

Comments tweaked by tabbott.

Closes: #7032.

timabbott/zulip,rht/zulip,kou/zulip,showell/zulip,rishig/zulip,synicalsyntax/zulip,punchagan/zulip,showell/zulip,zulip/zulip,kou/zulip,eeshangarg/zulip,timabbott/zulip,andersk/zulip,brainwane/zulip,hackerkid/zulip,tommyip/zulip,hackerkid/zulip,andersk/zulip,hackerkid/zulip,eeshangarg/zulip,timabbott/zulip,shubhamdhama/zulip,eeshangarg/zulip,shubhamdhama/zulip,eeshangarg/zulip,rht/zulip,rht/zulip,synicalsyntax/zulip,synicalsyntax/zulip,timabbott/zulip,brainwane/zulip,tommyip/zulip,eeshangarg/zulip,timabbott/zulip,tommyip/zulip,andersk/zulip,brainwane/zulip,punchagan/zulip,hackerkid/zulip,tommyip/zulip,rht/zulip,rishig/zulip,timabbott/zulip,shubhamdhama/zulip,rishig/zulip,shubhamdhama/zulip,showell/zulip,rishig/zulip,rishig/zulip,rishig/zulip,hackerkid/zulip,brainwane/zulip,andersk/zulip,hackerkid/zulip,hackerkid/zulip,punchagan/zulip,kou/zulip,tommyip/zulip,kou/zulip,kou/zulip,showell/zulip,showell/zulip,shubhamdhama/zulip,showell/zulip,andersk/zulip,rht/zulip,tommyip/zulip,eeshangarg/zulip,zulip/zulip,kou/zulip,punchagan/zulip,punchagan/zulip,andersk/zulip,synicalsyntax/zulip,zulip/zulip,zulip/zulip,zulip/zulip,synicalsyntax/zulip,synicalsyntax/zulip,rht/zulip,punchagan/zulip,rht/zulip,eeshangarg/zulip,shubhamdhama/zulip,brainwane/zulip,shubhamdhama/zulip,andersk/zulip,zulip/zulip,tommyip/zulip,rishig/zulip,brainwane/zulip,punchagan/zulip,showell/zulip,kou/zulip,timabbott/zulip,zulip/zulip,brainwane/zulip,synicalsyntax/zulip