CASMCMS-8713: Temporarily modify PyYAML, kubernetes install procedure

[mharding-hpe]

Summary and Scope

Cray Product Catalog builds started failing recently, due to yaml/pyyaml#601. Because CPC is using an Alpine container, and because the kubernetes Python module has a dependency on PyYAML >= 5.4, this PR represents the simplest workaround I was able to come up with. (Essentially, it forces the install of PyYAML inside the Docker container to use an older version of Cython). The PR is careful to only make this change when installing the PyYAML module and (because it has a dependency on PyYAML) the kubernetes module. I tried doing it with the modification limited to the PyYAML module, but the problem persisted until I pulled the kubernetes module in as well.

This should only be a temporary workaround. There is a PR up for PyYAML that will allow us to remove this workaround, but it's not clear when it will be merged and released. That PR is: yaml/pyyaml#702

This CPC workaround PR should have no functional impact on CPC. It will just allow the builds to continue working.

Issues and Related PRs

• "AttributeError: cython_sources" with Cython 3.0.0a10 yaml/pyyaml#601
• Pin Cython build constraint to < 3.0 yaml/pyyaml#702
• Works around build failures documented in CASMCMS-8713

Testing

None beyond making sure the build worked (which itself includes a run of the regression tests).

Risks and Mitigations

Without this, the CPC is unbuildable.