flux-uri(1) pid resolver does not work on macos

[garlick]

Problem: the flux-uri(1) pid resolver relies on /proc but that does not exist on macos

$ flux uri
flux-uri: ERROR: No such file or directory: '/proc/65570/task'

[grondo]

It appears perhaps ps -Eww may be able to get the environment for a target PID on macos. However, when the target is a broker, the pid resolver has to attempt to find a child, since FLUX_URI is not set in the broker itself.

Since it would be a bit of work to get this working on macos, and the pid resolver is not necessary functionality (and also we don't have any immediate need for Flux on macos afaik) I'd be inclined to leave this as is or maybe just detect macos and emit a "not supported" error.

Unfortunately this means we're going to have to disable a bunch of tests on macos, maybe by adding a new test prereq NOT_MACOS or similar? Hopefully that would be less work than getting the pid resolver (and anything else that uses /proc) working.

[garlick]

Fine with me. I mainly just wanted to get some issues open for macos so interested parties could dig in should they choose. Not a priority.

[grondo]

Sounds good. Maybe we want to create a macos label for these?

[garlick]

Good idea, I'll do that.