There was no documentation to move back into the netbox folder after installing/configuring nginx. You would move into nginx on line 42 then try and figure out why you couldn't copy gunicorn on line 113.
-Copy `contrib/gunicorn.py` to `/opt/netbox/gunicorn.py`. We make a copy of this file to ensure that any changes to it do not get overwritten by a future upgrade.
+Copy `/opt/netbox/contrib/gunicorn.py` to `/opt/netbox/gunicorn.py`. We make a copy of this file to ensure that any changes to it do not get overwritten by a future upgrade.