ensure summary kernel entry populated

Author: bjlittle

pytest_mpl/plugin.py

@@ -621,6 +621,7 @@ def compare_image_to_hash_library(self, item, fig, result_dir, summary=None):
         hash_name = self.generate_test_name(item)
         baseline_hash = hash_library.get(hash_name, None)
         summary['baseline_hash'] = baseline_hash
+        summary['kernel'] = self.kernel.name
 
         result_hash = self.generate_image_hash(item, fig)
         summary['result_hash'] = result_hash