04/07 Update: For latest updates you can refer to issue here.
Apologies for the breaking changes that this issue has caused for your applications.
Oryx has pre-installed Python SDKs on the build images; if the SDK that your application is targeting is not a part of this set, Oryx will fallback to dynamic installation, which attempts to pull a Python SDK that meets your application's requirements from our storage account, where we backup a variety of Python SDKs.
In this case, it appears that the Python 3.9.12 SDK was published to our storage account yesterday around 3:10 PM PST (10:10 PM UTC), and applications targeting Python 3.9 are now pulling down this 3.9.12 SDK rather than the previously published 3.9.7 SDK.
I'm optimistic that we should have this resolved in the next couple of hours, but in the meantime, as folks have mentioned above, if you are able to downgrade your application to using Python 3.8, please consider doing so. Alternatively, if your build/deployment method allows you to snap to a specific patch version of Python, please consider targeting Python 3.9.7, which was the previous 3.9.* version that can be pulled down during dynamic installation.
Again, apologies for the issues that this has caused you all.