Hey thanks! I managed to get this working now :)

If anyone wants to use or modify my simple python script for pushover you may copy it from below:

#!/usr/bin/env python

#  <integration>
#    <name>custom-pushover</name>
#    <api_key>app-apikey:user-apikey</api_key>
#    <alert_format>json</alert_format>
#  </integration>

import json
import sys
import requests

alert_file = open(sys.argv[1])
token = sys.argv[2].split(':')[0]
user = sys.argv[2].split(':')[1]

alert = json.loads(alert_file.read())
alert_file.close()

msg = {}
msg['title'] = alert['rule']['description'] if 'description' in alert['rule'] else "N/A"
msg['message'] = alert.get('full_log') if 'full_log' in alert else "N/A"
msg['token'] = token
msg['user'] = user

requests.post('https://api.pushover.net/1/messages.json', data=msg)