Make CI resolve the Python 3.15 release candidate

3.15 is still a pre-release: conda-forge gates it behind the python_rc
label and actions/setup-python has no stable 3.15 yet.

- Add conda-forge/label/python_rc to the conda env channels and to the
  conda build/install channel lists (conda-package, conda-package-cf,
  build_pip).
- Set allow-prereleases: true for setup-python in both clang workflows.
- Add fail-fast: false to build_pip and the clang workflows so a 3.15
  failure no longer cancels the other Python jobs.

These RC accommodations should be reverted once 3.15 is final.

Author: antonwolfy

.github/workflows/build-with-clang.yml

@@ -14,6 +14,7 @@ jobs:
     runs-on: ubuntu-latest
 
     strategy:
+      fail-fast: false
       matrix:
         python: ["3.10", "3.11", "3.12", "3.13", "3.14", "3.14t", "3.15"]
 
@@ -47,6 +48,8 @@ jobs:
         uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
         with:
           python-version: ${{ matrix.python }}
+          # allow the 3.15 release candidate until 3.15 is final
+          allow-prereleases: true
           architecture: x64
 
       - name: Checkout repo

.github/workflows/build-with-standard-clang.yml

@@ -13,6 +13,7 @@ jobs:
     runs-on: ubuntu-latest
 
     strategy:
+      fail-fast: false
       matrix:
         python: ["3.10", "3.11", "3.12", "3.13", "3.14", "3.14t", "3.15"]
 
@@ -38,6 +39,8 @@ jobs:
         uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
         with:
           python-version: ${{ matrix.python }}
+          # allow the 3.15 release candidate until 3.15 is final
+          allow-prereleases: true
           architecture: x64
 
       - name: Checkout repo

.github/workflows/build_pip.yml

@@ -17,6 +17,7 @@ jobs:
         shell: bash -el {0}
 
     strategy:
+      fail-fast: false
       matrix:
         python: ["3.10", "3.11", "3.12", "3.13"]
         include:
@@ -36,7 +37,8 @@ jobs:
       - uses: conda-incubator/setup-miniconda@8ee1f361103df19b6f8c8655fd3967a8ecb162d5 # v4.0.1
         with:
           miniforge-version: latest
-          channels: conda-forge
+          # python_rc label carries the 3.15 release candidate; drop once 3.15 is final
+          channels: conda-forge,conda-forge/label/python_rc
           activate-environment: test
           python-version: ${{ matrix.python }}
 

.github/workflows/conda-build-test.yml

@@ -81,7 +81,8 @@ jobs:
         with:
           miniforge-version: latest
           activate-environment: ${{ env.build-env-name }}
-          channels: conda-forge
+          # python_rc label carries the 3.15 release candidate; drop once 3.15 is final
+          channels: conda-forge,conda-forge/label/python_rc
           python-version: ${{ matrix.python }}
 
       - name: Cache conda packages
@@ -173,7 +174,8 @@ jobs:
         uses: conda-incubator/setup-miniconda@8ee1f361103df19b6f8c8655fd3967a8ecb162d5 # v4.0.1
         with:
           miniforge-version: latest
-          channels: conda-forge
+          # python_rc label carries the 3.15 release candidate; drop once 3.15 is final
+          channels: conda-forge,conda-forge/label/python_rc
           activate-environment: ${{ env.test-env-name }}
           python-version: ${{ matrix.python }}
 

.github/workflows/conda-package-cf.yml

@@ -21,7 +21,7 @@ jobs:
       runs-on: ubuntu-latest
       conda-subdir: linux-64
       pkgs-dir: /home/runner/conda_pkgs_dir
-      channels-list: -c conda-forge --override-channels
+      channels-list: -c conda-forge -c conda-forge/label/python_rc --override-channels
       recipe-dir: conda-recipe-cf
 
   windows:
@@ -31,7 +31,7 @@ jobs:
       runs-on: windows-latest
       conda-subdir: win-64
       pkgs-dir: D:\conda_pkgs_dir
-      channels-list: -c conda-forge --override-channels
+      channels-list: -c conda-forge -c conda-forge/label/python_rc --override-channels
       recipe-dir: conda-recipe-cf
 
   osx:
@@ -41,5 +41,5 @@ jobs:
       runs-on: macos-26-intel
       conda-subdir: osx-64
       pkgs-dir: /Users/runner/conda_pkgs_dir
-      channels-list: -c conda-forge --override-channels
+      channels-list: -c conda-forge -c conda-forge/label/python_rc --override-channels
       recipe-dir: conda-recipe-cf

.github/workflows/conda-package.yml

@@ -21,7 +21,7 @@ jobs:
       runs-on: ubuntu-latest
       conda-subdir: linux-64
       pkgs-dir: /home/runner/conda_pkgs_dir
-      channels-list: -c https://software.repos.intel.com/python/conda -c conda-forge --override-channels
+      channels-list: -c https://software.repos.intel.com/python/conda -c conda-forge -c conda-forge/label/python_rc --override-channels
       recipe-dir: conda-recipe
       build-wheels: true
 
@@ -32,6 +32,6 @@ jobs:
       runs-on: windows-latest
       conda-subdir: win-64
       pkgs-dir: D:\conda_pkgs_dir
-      channels-list: -c https://software.repos.intel.com/python/conda -c conda-forge --override-channels
+      channels-list: -c https://software.repos.intel.com/python/conda -c conda-forge -c conda-forge/label/python_rc --override-channels
       recipe-dir: conda-recipe
       build-wheels: true