Builds failing for Python 3.11: no compatible `rapids-xgboost`

[jameslamb]

Description

On 26.08 and 26.10 nightlies, seeing failures like this:

error    libmamba Could not solve for environment specs
    The following packages are incompatible
    ├─ cuda-version =12.9 * is requested and can be installed;
    ├─ python =3.11 * is requested and can be installed;
    └─ rapids =26.8 * is not installable because there are no viable options
       ├─ rapids 26.08.00a13 would require
       │  └─ rapids-xgboost =26.8 * but there are no viable options
       │     ├─ rapids-xgboost 26.08.00a13 would require
       │     │  └─ xgboost =3.3.0 rapidsai_py*, which requires
       │     │     └─ python >=3.12 * but there are no viable options
       │     │        ├─ python [3.12.0|3.12.1|...|3.14.6] conflicts with any installable versions previously reported;
       │     │        └─ python [3.14.0rc1|3.14.0rc2|3.14.0rc3] would require
       │     │           └─ _python_rc =* *, which does not exist (perhaps a missing channel);
       │     └─ rapids-xgboost 26.08.00a13 would require
       │        └─ cuda-version >=13,<14.0a0 *, which conflicts with any installable versions previously reported;
       └─ rapids 26.08.00a13 would require
          └─ cuda-version >=13,<14.0a0 *, which conflicts with any installable versions previously reported.

https://github.com/rapidsai/integration/actions/runs/30252791828

Reproducible example

This is breaking builds all Python 3.11 builds on release/26.08 and main here and over in https://github.com/rapidsai/docker

Notes

This is happening because rapidsai/xgboost-feedstock#139 bumped rapids-xgboost to v3.3.0, which only supports Python >=3.12.

[chyunsu3]

I am testing XGBoost 3.3 with Python 3.11 here: dmlc/xgboost#12374. I'm hoping to create a minimal patch for XGBoost 3.3 to make it work with Python 3.11.