Starting bottle web server through systemd?

Question

I am trying to start a bottle web app I wrote using systemd. I made the file /etc/systemd/user/bottle.service with the following contents:

[Unit]
Description=Bottled fax service
After=syslog.target

[Service]
Type=simple
User=fax
Group=fax
WorkingDirectory=/home/fax/bottlefax/
ExecStart=/usr/bin/env python3 server.py
StandardOutput=syslog
StandardError=syslog
Restart=always
RestartSec=2

[Install]
WantedBy=bottle.target

However, when I try to start it, it fails and this is printed in journalctl:

Jun 10 17:33:31 nano systemd[1]: Started Bottled fax service.
Jun 10 17:33:31 nano systemd[1]: Starting Bottled fax service...
Jun 10 17:33:31 nano systemd[2380]: Failed at step GROUP spawning /usr/bin/env: No such process
Jun 10 17:33:31 nano systemd[1]: bottle.service: main process exited, code=exited, status=216/GROUP
Jun 10 17:33:31 nano systemd[1]: Unit bottle.service entered failed state.
Jun 10 17:33:31 nano systemd[1]: bottle.service failed.

How should I fix this?

Edit:

Changing to /usr/bin/python3 as others have suggested results in the same error (changed file though):

Jun 10 18:43:48 nano systemd[1]: Started Bottled fax service.
Jun 10 18:43:48 nano systemd[1]: Starting Bottled fax service...
Jun 10 18:43:48 nano systemd[2579]: Failed at step GROUP spawning /usr/bin/python3: No such process
Jun 10 18:43:48 nano systemd[1]: bottle.service: main process exited, code=exited, status=216/GROUP
Jun 10 18:43:48 nano systemd[1]: Unit bottle.service entered failed state.
Jun 10 18:43:48 nano systemd[1]: bottle.service failed.

Answer 1

I would have commented but I can't :/

Have you tried something like with an absolute path ?

ExecStart=/usr/bin/python3 /path/to/your/server.py

That's the only issue I can see here.