[CI] added matplotlib for tests

Author: KrisThielemans

.appveyor.yml

@@ -36,7 +36,7 @@ build_script:
   - echo Using Miniconda %MINICONDA%
   - "set PATH=%MINICONDA%;%MINICONDA%\\Scripts;%MINICONDA%\\Library\\bin;%PATH%"
   # install parallelproj and Python stuff
-  - conda install -c conda-forge  -yq libparallelproj swig numpy pytest
+  - conda install -c conda-forge  -yq libparallelproj swig numpy pytest matplotlib
   - CALL conda.bat activate base
   - python --version
   - mkdir build

.github/workflows/build-test.yml

@@ -235,10 +235,10 @@ jobs:
               # brew install openblas
               # export OPENBLAS=$(brew --prefix openblas)
               #python -m pip install --no-cache-dir --no-binary  numpy numpy # avoid the cached .whl!
-              python -m pip install numpy pytest
+              python -m pip install numpy pytest matplotlib
               ;;
             (*)
-              python -m pip install numpy pytest
+              python -m pip install numpy pytest matplotlib
               ;;
           esac