Note: you only see the Deprecation warning during build if the gpg build
fails.

You can force the error using

  RUN PYTHONWARNINGS="error" pip install --no-cache-dir gpg --no-build-
isolation

in the Dockerfile.

Also Roundup requires setuptools >= 78.1.1 so the SPDX license format is
supported in all
recent Roundup builds and Roundup uses that format in setup.py:

          license_expression="MIT AND ZPL-2.0 AND PSF-2.0",