Use iiasa/actions to set up GAMS

.github/workflows/pytest.yaml

@@ -7,7 +7,6 @@ on:
     branches: [ main ]
 
 env:
-  GAMS_VERSION: 25.1.1
   # For setuptools-scm. With fetch --tags below, this ensures that enough
   # history is fetched to contain the latest tag, so that setuptools-scm can
   # generate the version number. Update:
@@ -91,20 +90,10 @@ jobs:
           ${{ matrix.os }}-gams${{ env.GAMS_VERSION }}-
           ${{ matrix.os }}-
 
-    - name: Install GAMS
-      # Use the scripts from the checked-out ixmp repo
-      env:
-        CI_OS: ${{ matrix.os }}
-      run: ixmp/ci/install-gams.sh
-      shell: bash
-
-    - name: Install GAMS license
-      env:
-        GAMS_LICENSE: ${ secrets.GAMS_LICENSE }
-      run: |
-        echo "$GAMS_LICENSE" > $(dirname $(which gams))/gamslice.txt
-        gams
-      shell: bash
+    - uses: iiasa/actions/setup-gams@main
+      with:
+        version: 25.1.1
+        license: ${{ secrets.GAMS_LICENSE }}
 
     - name: Upgrade pip, wheel, setuptools-scm
       run: python -m pip install --upgrade pip wheel setuptools-scm