File: On errors with DirFds, print the path to the directory.

[nh2]

Example: Turns errors like

openAnonymousTempFileFromDir: permission denied (Permission denied)

into

openAnonymousTempFileFromDir: /tmp/unwritable-test-dir1218657: permission denied (Permission denied)

so that the user can see for which directory write permissions are missing.

---

I found it difficult to figure errors in production if I am not told where e.g. permission errors lie without this.

[snoyberg]

Looks like this is failing on Mac

[nh2]

From the error message, I haven't managed yet to figure out why it's failing. It says

predicate failed on expected exception: IOException (/private/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/unwritable-test-dir23032: openBinaryTempFile: permission denied (Permission denied))

which looks to me like the full path /private/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/unwritable-test-dir23032 is present in the exception (which is what the test ist checking).