nitpick: I'm generally not a fan of putting tty.info(...) in source files other than cmd/*.py, since non-cmd/*.py files have other entrypoints where no terminal is involved at all (e.g. user scripts that call binary_distribution.push(...)).

Alternatively, can you make:

1. def push(spec: spack.spec.Spec) -> Result accept just an individual spec and let it return whether it succeeded and if so where it pushed the spec?
2. def push_all(*spec: spack.spec.Spec) -> List[Result] do basically return [push(s) for s in specs]
3. Make cmd/buildcache.py do the logic of listing the specs that can be pushed to the cache.
4. Make CI just call push(...) so it's very clear it will only ever push one spec.

Then the tty.info business can go into cmd/buildcache.py and cmd/ci.py.

This also ties in with #35601 since error handling can be improved too. Maybe push_all could instead return a List[Either[Result, Error]] by catching errors in push.

Make CI just call push(...) so it's very clear it will only ever push one spec.

This is the bit I thought was really key from your review, thanks. Let me know if I missed the mark in your opinion, I didn't really see the benefit of a push_all, but could still be convinced.

I've hijacked this PR to improve the UI more generally, cause it was still extremely verbose in some cases. Now it looks like this:

@spackbot run pipeline

I encountered an error attempting to run the pipeline.

Error: <class 'aiohttp.client_exceptions.ContentTypeError'>, 0, message='Attempt to decode JSON with unexpected mimetype: text/html', url=URL('https://gitlab.spack.io/api/v4/projects/2/repository/commits/pr36141_print-msg-for-each-pushed-buildcache')
Stack trace:
  File "/usr/local/lib/python3.7/site-packages/rq/worker.py", line 1359, in perform_job
    rv = job.perform()
  File "/usr/local/lib/python3.7/site-packages/rq/job.py", line 1178, in perform
    self._result = self._execute()
  File "/usr/local/lib/python3.7/site-packages/rq/job.py", line 1218, in _execute
    coro_result = loop.run_until_complete(result)
  File "/usr/local/lib/python3.7/asyncio/base_events.py", line 587, in run_until_complete
    return future.result()
  File "./spackbot/workers.py", line 197, in run_pipeline_task
    if not await check_gitlab_has_latest(branch, head_sha, gh, comments_url):
  File "./spackbot/workers.py", line 77, in check_gitlab_has_latest
    gitlab_commit = await helpers.get(commit_url, headers)
  File "./spackbot/helpers.py", line 202, in get
    return await response.json()
  File "/usr/local/lib/python3.7/site-packages/aiohttp/client_reqrep.py", line 1110, in json
    headers=self.headers,

@spackbot run pipeline

I've started that pipeline for you!

@haampie Feel free to merge, if this seems ready. All the points in my previous review seem addressed, so ✔️