Add imports for dummy viewer test

Author: mwcraig

tests/test_astro_image_display_api.py

@@ -1,7 +1,8 @@
 from astropy.utils.data import get_pkg_data_contents
 
 from astro_image_display_api.interface_definition import ImageViewerInterface
-
+from astro_image_display_api.widget_api_test import ImageWidgetAPITest
+from astro_image_display_api.dummy_viewer import ImageViewer
 
 def test_api_test_class_completeness():
     """