shutil.copystat() fails inside Docker on Azure - python-3.x

Question

The failing code runs inside a Docker container based on python:3.6-stretch debian.
It happens while Django moves a file from one Docker volume to another.
When I test on MacOS 10, it works without error. Here, the Docker containers are started with docker-compose and use regular Docker volumes on the local machine.
Deployed into Azure (AKS - Kubernetes on Azure), moving the file succeeds but copying the stats fails with the following error:
File "/usr/local/lib/python3.6/site-packages/django/core/files/move.py", line 70, in file_move_safe
copystat(old_file_name, new_file_name)
File "/usr/local/lib/python3.6/shutil.py", line 225, in copystat
_copyxattr(src, dst, follow_symlinks=follow)
File "/usr/local/lib/python3.6/shutil.py", line 157, in _copyxattr
names = os.listxattr(src, follow_symlinks=follow_symlinks)
OSError: [Errno 38] Function not implemented: '/some/path/file.pdf'
The volumes on Azure are persistent volume claims with ReadWriteMany access mode.
Now, copystat is documented as:
copystat() never returns failure.
https://docs.python.org/3/library/shutil.html
My questions are:
Is this a "bug" because the documentation says that it should "never return failure"?
Can I savely try/except this error because the file in question is moved (it only fails later on, while trying to copy the stats)
Can I change something about the Azure settings that fix this? (probably not)
Here some small test on the machine in Azure itself:
root:/media/documents# ls -al
insgesamt 267
drwxrwxrwx 2 1000 1000 0 Jul 31 15:29 .
drwxrwxrwx 2 1000 1000 0 Jul 31 15:29 ..
-rwxrwxrwx 1 1000 1000 136479 Jul 31 16:48 orig.pdf
-rwxrwxrwx 1 1000 1000 136479 Jul 31 15:29 testfile
root:/media/documents# lsattr
--S-----c-jI------- ./orig.pdf
--S-----c-jI------- ./testfile
root:/media/documents# python
Python 3.6.6 (default, Jul 17 2018, 11:12:33)
[GCC 6.3.0 20170516] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import shutil
>>> shutil.copystat('orig.pdf', 'testfile')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python3.6/shutil.py", line 225, in copystat
_copyxattr(src, dst, follow_symlinks=follow)
File "/usr/local/lib/python3.6/shutil.py", line 157, in _copyxattr
names = os.listxattr(src, follow_symlinks=follow_symlinks)
OSError: [Errno 38] Function not implemented: 'orig.pdf'
>>> shutil.copystat('orig.pdf', 'testfile', follow_symlinks=False)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python3.6/shutil.py", line 225, in copystat
_copyxattr(src, dst, follow_symlinks=follow)
File "/usr/local/lib/python3.6/shutil.py", line 157, in _copyxattr
names = os.listxattr(src, follow_symlinks=follow_symlinks)
OSError: [Errno 38] Function not implemented: 'orig.pdf'
>>>

Answer 1

The following solution is a hotfix. It would have to be applied to any method that calls copystat directly or indirectly (or any shutil method that produces an ignorable errno.ENOSYS).
if hasattr(os, 'listxattr'):
LOGGER.warning('patching listxattr to avoid ERROR 38 (errno.ENOSYS)')
# avoid "ERROR 38 function not implemented on Azure"
with mock.patch('os.listxattr', return_value=[]):
file_field.save(name=name, content=GeneratedFile(fresh, content_type=content_type), save=True)
else:
file_field.save(name=name, content=GeneratedFile(fresh, content_type=content_type), save=True)
file_field.save is the Django method that calls the shutil code in question. It's the last location in my code before the error.