Signaling an error while saving files due to file-extended-attributes

[Eli Zaretskii]

Emacs 26 silently returned nil when file-acl or file-selinux-context
failed for a file.  Emacs 27 signals an error in that case (except
when the error returned by the low-level APIs are one of a small set
of errors that are taken as evidence that extended attributes are not
supported for the file).

This is probably OK for the primitives that access the extended
attributes, but what about their calls during saving a buffer to its
file?  Signaling an error there effectively prevents users from saving
their edits in such cases, which IMO makes little sense.

So how about wrapping the call to file-extended-attributes in
backup-buffer with '(ignore-error file-error ...)' ?  Are there any
potential problems with that in the context of saving a buffer?