CI: test different mpmath

We want the matrix to have empty mpmath in most cases, in case SymPy has
pins.

Author: cbm755

.github/workflows/main.yml

@@ -87,25 +87,42 @@ jobs:
       matrix:
         octave: [10.3.0]
         sympy: [1.9, 1.10.1, 1.11.1, 1.12.1, 1.13.0, 1.13.3, 1.14.0]
+        mpmath: [""]  # blank means SymPy pin in effect
         include:
           - octave: 10.2.0
             sympy: 1.14.0
+            mpmath:
           - octave: 10.1.0
             sympy: 1.14.0
+            mpmath:
           - octave: 9.4.0
             sympy: 1.14.0
+            mpmath:
           - octave: 9.3.0
             sympy: 1.14.0
+            mpmath:
           - octave: 9.2.0
             sympy: 1.14.0
+            mpmath:
           - octave: 9.1.0
             sympy: 1.14.0
+            mpmath:
+          - octave: 10.3.0
+            sympy: 1.14.0
+            mpmath: 1.4.0
+          - octave: 10.3.0
+            sympy: 1.14.0
+            mpmath: 1.3.0
+          - octave: 10.3.0
+            sympy: 1.14.0
+            mpmath: 1.2.1
     steps:
       - uses: actions/checkout@v5
       - name: Container setup
         env:
           OCT: ${{ matrix.octave }}
           SYMPY: ${{ matrix.sympy }}
+          MPMATH: ${{ matrix.mpmath }}
         run: |
           uname -a
           docker pull docker.io/gnuoctave/octave:$OCT
@@ -121,6 +138,10 @@ jobs:
           echo $A
           docker exec oc pip install --break-system-packages packaging
           docker exec oc pip install --break-system-packages sympy==$SYMPY
+          echo $MPMATH
+          if [[ -n "$MPMATH" ]]; then
+            docker exec oc pip install --break-system-packages mpmath==$MPMATH
+          fi
           docker exec oc octave-cli --eval "pkg install -forge doctest"
       - name: Run BIST in-place
         run: docker exec oc make -C octsympy test