Check pip-compile failed to resolve requirements

[reiyw]

PR Checklist

Please check if your PR fulfills the following requirements:

• Does not include precompiled binaries, eg. .par files. See CONTRIBUTING.md for info
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature (please, look at the "Scope of the project" section in the README.md file)
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

Issue Number: #478

When pip-compile fails to resolve the dependency, requirements_test will pass regardless of the content of the lock file.

What is the new behavior?

When pip-compile fails to resolve the dependency, exit with an error message, and the test will fail.

Does this PR introduce a breaking change?

• Yes
• No

Other information

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[reiyw]

@googlebot I signed it!

[thundergolfer]

Suggested adding extra error checking, but happy with the contributed fix 🙏

[thundergolfer]

This improves things for sure, but still leaves us open to cases where e.code not in {0, 2}. Looking at the piptools source, it only ever exits 0 or 2, but my preference would be to check for the unexpected cases and exit(1) instead of incorrectly succeeding .

if e.code == 2:
   # handle 2
   # ...
   sys.exit(1)
elif e.code == 0:
   # handle 0
   # ...
   sys.exit(0)
else:
   # handle unexpected
   # ...
   sys.exit(1)

[reiyw]

I totally agree. I have fixed it that way.

[thundergolfer]

Thanks for the contribution 👍