Try to fix an error that occurs since 3 days (#2224)

Author: hansthen

.github/workflows/test_code.yml

@@ -26,6 +26,7 @@ jobs:
     - name: Setup Micromamba env
       uses: mamba-org/setup-micromamba@v3
       with:
+        micromamba-version: '2.6.0-0'
         environment-name: TEST
         create-args: >-
           python=${{ matrix.python-version }}