fly deploy shows no machines

[tvdfly]

Describe the bug We run fly deploy in buildkite. They handle some control characters correctly, and I guess they can't handle the fancy output of fly deploy.

this is what fly deploy shows during and after deployments:

fly deploy
  | ==> Verifying app config
  | Validating fly.toml
  | Platform: machines
  | ✓ Configuration is valid
  | --> Verified app config
  | ==> Building image
  | Searching for image 'registry.fly.io/app:tag' locally...
  | Searching for image 'registry.fly.io/app:tag' remotely...
  | image found: img_19<redacted>
  |  
  | Watch your deployment at https://fly.io/apps/app/monitoring
  |  
  |  
  | -------
  | Updating existing machines in 'app' with rolling strategy
  |  
  |  
  | -------
  |  
  | Visit your newly deployed app at http://app.fly.dev/
 

that's mostly fine when deployments work. it's a bit of a problem when they fail, because the specific machines and error messages don't show up:

fly deploy
==> Verifying app config
  | Validating fly.toml
  | Platform: machines
  | ✓ Configuration is valid
  | --> Verified app config
  | ==> Building image
  | Searching for image 'registry.fly.io/app:tag' locally...
  | Searching for image 'registry.fly.io/app:tag' remotely...
  | image found: img_<redacted>
  |  
  | Watch your deployment at https://fly.io/apps/app/monitoring
  |  
  |  
  | -------
  | Updating existing machines in 'app' with rolling strategy
  |  
  |  
  | -------
  | Error 127
  | 🚨 Error: The command exited with status 2

I can use fly deploy | tee to work around this, which forces flyctl into the non-fancy output.

Expected behavior: fly deploy outputs information about machines being updated and shows error messages when run on a buildkite build agent.