I've looked a bit into this and it seems like ESTALE can be caused in two cases:

 - Under WPAR environment
https://www.ibm.com/docs/en/aix/7.1?topic=aix-wpar-concepts

https://www.ibm.com/support/pages/apar/IV50544
> When using WPAR setup under AIX, with each WPAR configured as an NFS client, it is possible that asynchronous READDIR operations fail with ESTALE error

 - http://www.audentia-gestion.fr/IBM/PDF/basetrf2_pdf.pdf
ESTALE. The process's root or current directory is located in a virtual file system that has been unmounted.


In the first case, the solution given is to run READDIR under a different CID. I've found the definition of CID just 10 minutes ago but now can't find it again :(. Anyway, it seems to be an ID corresponding to the WPAR environment.

In the 2nd case, it's pretty clear that we shouldn't silence it: if you unmount a virtual partition while running rmtree on it, I'm 99.9% sure it was unintended!

In the first case, I don't think Python has any specific support for WPAR? Maybe? If not, we shouldn't do anything, if yes, maybe it can be fixed to handle this.

It sounds like Ronal may have ran into the first case, or something else entirely.