feat: Tell the user when we can't remove the image if it's in use (#406)

Signed-off-by: Dan Webb <[email protected]>
Co-authored-by: Edward Smith <[email protected]>

lib/kitchen/docker/helpers/image_helper.rb

@@ -41,7 +41,16 @@ def parse_image_id(output)
 
         def remove_image(state)
           image_id = state[:image_id]
-          docker_command("rmi #{image_id}")
+          if image_in_use?(state)
+            info("[Docker] Image ID #{image_id} is in use. Skipping removal")
+          else
+            info("[Docker] Removing image with Image ID #{image_id}.")
+            docker_command("rmi #{image_id}")
+          end
+        end
+
+        def image_in_use?(state)
+          docker_command("ps -a", suppress_output: !logger.debug?).include?(state[:image_id])
         end
 
         def build_image(state, dockerfile)