I have updated python version manually to 3.7.3 on OctoPi 0.17. A recent update request for 1.7.2 is still complaining about python version isn't supported for direct update.
It's actually your pip version that is outdated - how long ago did you run the upgrade script? It should upgrade pip if you've done it recently in the last week and a half, since I realised this was an issue.
Regardless, you should be able to follow the instructions linked from where it says the Python environment is outdated
It's the first entry on the list, under 'update your environment'.