Handle missing token errors

[heff]

• Start a project with no Mux creds anywhere, i.e. no env.local
• Add a video to /videos
• Run next-video sync

It'd be good to handle this as a known error in next-video, rather than unknown from mux-node, and maybe directly people back to that part of the next-video docs.

[mmcc]

This doesn't look like an up to date error, we added a big try/catch there a little while ago. I'm not sure what we should do here re: known errors, that kind of integration-specific stuff sits a level below the CLI in the handlers.

[luwes]

I got the same error as @heff.

from this line

next-video/src/cli/sync.ts

Line 128 in 962a0f0

log.error('An unknown error occurred', err);

should be easy to make it known if it comes from @mux/node in the stack trace

[heff]

Maybe related, it'd be nice to provide a bit nicer message when a user doesn't set up their creds correctly. I intentionally broke my creds and got this. It's not bad but could be more helpful, and I expect this to be a common issue.