Fix issue with windows and matplolib (#470)

* Empty commit for test

* fix error on windows

* config only with matplolib

* fix str

* try to fix the import

Author: lionelkusch

test/conftest.py

@@ -3,6 +3,17 @@
 
 from hidimstat._utils.scenario import multivariate_simulation
 
+try:
+    import matplotlib
+except ImportError:
+    matplotlib = None
+
+
+def pytest_configure(config):  # noqa: ARG001
+    """Use Agg so that no figures pop up."""
+    if matplotlib is not None:
+        matplotlib.use("Agg", force=True)
+
 
 @pytest.fixture
 def data_generator(