Fix ImportError with Pillow under Windows(#175)

See msys2/MINGW-packages#11103 for related issues

.github/workflows/installation-from-remote.yaml

@@ -3,6 +3,8 @@ name: Install from repository
 on:
   schedule:
     - cron: '42 23 * * 3'  # every Wednesday at 23:42
+  pull_request:
+    types: [opened, reopened, edited, synchronize]
 
 jobs:
   build-conda-on-windows:
@@ -21,15 +23,18 @@ jobs:
       with:
         auto-update-conda: true
         auto-activate-base: true
-        activate-environment: ""
+        activate-environment: true
+        python-version: '3.10'
 
     - name: Install ConFlowGen
       run: |
+        conda info
         conda create -n test-install-conflowgen -c conda-forge conflowgen pytest
 
     - name: Run tests
       run: |
         conda activate test-install-conflowgen
+        pip install pillow==9.0.0
         python -m pytest --pyargs conflowgen
 
   build-conda-on-linux:
@@ -54,6 +59,7 @@ jobs:
       run: |
         conda init bash
         eval "$(conda shell.bash hook)"
+        conda info
         conda activate base
         conda create -n test-install-conflowgen -c conda-forge conflowgen pytest
 
@@ -86,6 +92,7 @@ jobs:
     - name: Install ConFlowGen
       run: |
         python -m pip install conflowgen pytest
+        python -m pip show --verbose conflowgen
 
     - name: Run tests
       run: |