for windows test : Use Non-GUI Backend for Matplotlib in Tests

Author: staskh

tests/test_plots.py

@@ -11,6 +11,8 @@
 from iglu_python.extension.plots import plot_daily, plot_statistics
 from iglu_python import load_libre
 
+import matplotlib
+matplotlib.use('Agg')
 
 @pytest.fixture(scope="module")
 def sample_cgm_data():