build PyYAML without build isolation

Author: t-vi

.github/workflows/ci-tests-fabric.yml

@@ -111,6 +111,7 @@ jobs:
           for fpath in `ls requirements/**/*.txt`; do \
             python ./adjust-torch-versions.py $fpath ${{ matrix.pytorch-version }}; \
           done
+          pip install "pyyaml==5.4" --no-build-isolation
 
       - name: pip wheels cache
         uses: actions/cache/restore@v4

.github/workflows/ci-tests-pytorch.yml

@@ -117,6 +117,7 @@ jobs:
             python ./adjust-torch-versions.py $fpath ${{ matrix.pytorch-version }}; \
           done
           cat requirements/pytorch/base.txt
+          pip install "pyyaml==5.4" --no-build-isolation
 
       - name: pip wheels cache
         uses: actions/cache/restore@v4