spread: fix python-hello

[mr-cal]

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• Have you signed the CLA?
• Have you successfully run ./runtests.sh static?
• Have you successfully run ./runtests.sh tests/unit?

---

setuptools-61.1.0 broke two spread tests:

• tests/spread/plugins/v2/build-and-run-hello:python_multiple_parts
• tests/spread/plugins/v2/build-and-run-hello:python_multiple_parts_staged

The following error is produced:

Successfully installed pip-22.0.4 setuptools-61.0.0 wheel-0.37.1
+ '[' -f setup.py ']'
+ pip install -U .
Processing /root/parts/hello/build
  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error

  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [14 lines of output]
      error: Multiple top-level packages discovered in a flat-layout: ['snap', 'empty'].

      To avoid accidental inclusion of unwanted files or directories,
      setuptools will not proceed with this build.

      If you are trying to create a single distribution with multiple packages
      on purpose, you should not rely on automatic discovery.
      Instead, consider the following options:

      1. set up custom discovery (`find` directive with `include` or `exclude`)
      2. use a `src-layout`
      3. explicitly set `py_modules` or `packages` with a list of names

      To find more information, look for "package discovery" on setuptools docs.
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.
Failed to build 'hello'.

Recommended resolution:
Check the build logs and ensure the part's configuration and sources are correct.
Run the same command again with --debug to shell into the environment if you wish to introspect this failure.

source: pypa/setuptools#2894

[codecov-commenter]

Codecov Report

Merging #3670 (d59a4c4) into main (ce1c558) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #3670   +/-   ##
=======================================
  Coverage   91.25%   91.25%           
=======================================
  Files         278      278           
  Lines       19396    19396           
=======================================
  Hits        17699    17699           
  Misses       1697     1697           

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