How to resolve (code=exited,status=203/Exec) while creating a system service for Flask app

Solution
[Unit]
Description=Flask web server

[Service]
User=schirag
PermissionsStartOnly=true
ExecStart=/usr/bin/python3 /home/schirag/server.py
TimeoutSec=600
Restart=on-failure
RuntimeDirectoryMode=755

[Install]
WantedBy=multi-user.target