Don't filter out ENOTSUP errors.
!!! error return
*** list non-xfs file (in /proc)
*** print attributes
!!! error return
*** list non-xfs file (in /proc)
*** print attributes
+<PROCFILE>: Operation not supported
+ !!! error return
*** list empty file
*** print attributes
*** query non-existant attribute
*** list empty file
*** print attributes
*** query non-existant attribute