Try skipping only the builds that have issues with scipy being involved.

.github/workflows/tests.yml

@@ -53,14 +53,11 @@ jobs:
           conda install -q -y cython>=0.26 "ipopt=${{ matrix.ipopt-version }}" numpy>=1.15 pkg-config>=0.29.2 setuptools>=39.0 pytest>=3.3.2
           conda list
           pytest
-      - name: Test with pytest and scipy
-        if: matrix.ipopt-version == '3.12'
-        run: |
-          conda install -q -y -c conda-forge cython>=0.26 "ipopt=${{ matrix.ipopt-version }}" numpy>=1.15 pkg-config>=0.29.2 setuptools>=39.0 pytest>=3.3.2 "scipy<1.10"
-          conda list
-          pytest
       - name: Test with pytest and scipy, new ipopt
-        if: matrix.ipopt-version != '3.12'
+        # cyipopt can build with these dependencies, but it seems impossible to
+        # also install scipy into these environments likely due to SciPy and
+        # Ipopt needed different libfortrans.
+        if: (matrix.ipopt-version != '3.12' && matrix.python-version != '3.11') || (matrix.ipopt-version != '3.12' && matrix.python-version != '3.10' && matrix.os != 'macos-latest')
         run: |
           conda install -q -y -c conda-forge cython>=0.26 "ipopt=${{ matrix.ipopt-version }}" numpy>=1.15 pkg-config>=0.29.2 setuptools>=39.0 pytest>=3.3.2 scipy>=0.19.0
           conda list