Branding patches cause issues with certain wheels

[SylvainCorlay]

This recipe patches the CPython source code to include conda-forge branding in the interpreter banner, namely | packaged by conda-forge |. However, since this banner is validated in platform.py (to prevent mismatches between the Python runtime and the python home in use), the platform.py is also patched for this validation to pass. Both patches are done in brand-python.py.

Now, I have the following issue with this: we are working on a PyPI wheel for the xeus-python jupyter kernel, for which we have a functional conda package, and which embeds Python. The conda package simply links with libpython.so and all is fine, but for the wheel, since we generally can't rely on Python distributions providing a libpython.so shared object, our PyPI manylinux wheel is statically linked with libpython.a. This causes the banner to not be the one from conda-forge an to cause a mismatch with conda-forge's patched validation regex.

To solve this issue, we would need to either renounce to the branding in the banner, or make the new regex slightly more flexible to also accept the original banner from the unpatched python interpreter.

cc @mingwandroid @jjhelmus @JohanMabille.