fix: distinguish docker build errors from streaming errors

[briandealwis]

In trying to reproduce #6126, I noticed that docker build errors are oddly prefixed with "unable to stream build output:".

Canceled build for leeroy-app
unable to stream build output: The command '/bin/sh -c exit 1' returned a non-zero code: 1. Please fix the Dockerfile and try again..

It turns out that the Docker code for parsing and interpreting the JSON message stream from the Docker daemon parses build failures as a JSONError object, which behaves like an error. This PR changes our error-handling code to return such errors directly.

[codecov]

Codecov Report

Merging #6910 (7cc83fb) into main (290280e) will decrease coverage by 1.64%.
The diff coverage is 63.63%.

@@            Coverage Diff             @@
##             main    #6910      +/-   ##
==========================================
- Coverage   70.48%   68.84%   -1.65%     
==========================================
  Files         515      551      +36     
  Lines       23150    25299    +2149     
==========================================
+ Hits        16317    17416    +1099     
- Misses       5776     6708     +932     
- Partials     1057     1175     +118     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/deploy.go	52.00% <ø> (-1.85%)	⬇️
cmd/skaffold/app/cmd/dev.go	84.61% <0.00%> (ø)
cmd/skaffold/app/cmd/render.go	36.66% <0.00%> (-4.72%)	⬇️
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/inspect_tests.go	62.50% <14.28%> (-1.14%)	⬇️
cmd/skaffold/app/cmd/fix.go	68.85% <40.00%> (-7.62%)	⬇️
cmd/skaffold/app/cmd/lint.go	42.85% <42.85%> (ø)
cmd/skaffold/app/cmd/find_configs.go	48.88% <50.00%> (+0.24%)	⬆️
cmd/skaffold/app/skaffold.go	76.19% <70.00%> (-8.43%)	⬇️
cmd/skaffold/app/cmd/inspect_build_env.go	65.11% <75.00%> (+6.39%)	⬆️
... and 170 more

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[briandealwis]

What's odd here is that this error can appear long after the output started. Maybe docker reports: is a better prefix?

[tejal29]

Not sure, why blocked label was added. Feel free to remove it!

[briandealwis]

I had it blocked pending the additional message.