Service starting gunicorn failing with "Start request repeated too quickly" - service

Question

Trying to start a service to run gunicorn as backend server for Flask, not working. Running nginx as frontend server for React, working.
Server:
Virtualization: vmware
Operating System: Red Hat Enterprise Linux 8.4 (Ootpa)
CPE OS Name: cpe:/o:redhat:enterprise_linux:8.4:GA
Kernel: Linux 4.18.0-305.3.1.el8_4.x86_64
Architecture: x86-64
Service file in /etc/systemd/system/myservice.service:
[Unit]
Description="Description"
After=network.target
[Service]
User=root
Group=root
WorkingDirectory=/home/project/app/api
ExecStart=/home/project/app/api/venv/bin/gunicorn -b 127.0.0.1:5000 api:app
Restart=always
[Install]
WantedBy=multi-user.target
/app/api:
-rwxr-xr-x. 1 root root 2018 Jun 9 20:06 api.py
drwxrwxr-x+ 5 root root 100 Jun 7 10:11 venv
Error message:
● myservice.service - "Description"
Loaded: loaded (/etc/systemd/system/myservice.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Thu 2021-06-10 19:01:01 CEST; 5s ago
Process: 18307 ExecStart=/home/project/app/api/venv/bin/gunicorn -b 127.0.0.1:5000 api:app (code=exited, status=203/EXEC)
Main PID: 18307 (code=exited, status=203/EXEC)
Jun 10 19:01:01 xxxx systemd[1]: myservice.service: Service RestartSec=100ms expired, scheduling restart.
Jun 10 19:01:01 xxxx systemd[1]: myservice.service: Scheduled restart job, restart counter is at 5.
Jun 10 19:01:01 xxxx systemd[1]: Stopped "Description".
Jun 10 19:01:01 xxxx systemd[1]: myservice.service: Start request repeated too quickly.
Jun 10 19:01:01 xxxx systemd[1]: myservice.service: Failed with result 'exit-code'.
Jun 10 19:01:01 xxxx systemd[1]: Failed to start "Description".
Tried, not working:
Adding Environment="PATH=/home/project/app/api/venv/bin" under [Service]
$ systemctl reset-failed myservice.service
$ systemctl daemon-reload
Reboot, ofc.
Tried, working:
Running (as root) /home/project/app/api/venv/bin/gunicorn -b 127.0.0.1:5000 api:app while in /app/api directory
Does anyone know how to fix this problem?

Answer 1

Typically enough, I figured it out shortly after posting this issue.
SELinux is messing with permissions for files and directories, so for anyone experiencing the same issue, make sure to test with the following alterings (as root):
$ setsebool -P httpd_can_network_connect on
$ chcon -Rt httpd_sys_content_t /path/to/your/Flask/dir
In my case: $ chcon -Rt httpd_sys_content_t /home/project/app/api
While this is NOT a permanent fix, it's worth a try. Check out the SELinux docs for more permanent solutions.