Introduce a "NotCapable" error

[caspervonb]

Right now we do not differentiate between errors raised by our sandbox and actual permission errors raised by the operating system (altho you can visually distinguish them if you squint and scan carefully for errno 13 which is EPERM).

I think WASI does this better in that it distinguishes between EPERM which is just errno EPERM and provides an additional extended errno enumeration member ENOTCAPABLE which is raised when the caller is not capable (it's a capability based sandboxing model) of performing an operation.

The benefit of separating these is that NotCapable (name subject to bike-shedding) is potentially a recoverable state; you can ask for permissions where-as PermissionDenied is just defacto this is not allowed and won't be allowed without external intervention.

[caspervonb]

This would be a fairly fundamental breaking change as current error instanceof checks would quietly start failing; so it would have to be for a 2.0 milestone.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[caspervonb]

Still very much something I want to change for 2.0, tag as suggestion please.

[hazae41]

👍 Sounds like HTTP errors Forbidden and Unauthorized