Make warning message checks more flexible

Author: mwcraig

astrowidgets/tests/widget_api_test.py

@@ -232,7 +232,7 @@ def test_click_drag(self):
         # If is_marking is true then trying to enable click_drag should fail
         self.image._is_marking = True
         self.image.click_drag = False
-        with pytest.raises(ValueError, match='Interactive marking'):
+        with pytest.raises(ValueError, match='[Ii]nteractive marking'):
             self.image.click_drag = True
         self.image._is_marking = False