code: def find_in_app(self, app, path):
          
          storage = self.storages.get(app, None)
          if storage:
              # only try to find a file if the source dir actually exists
              if storage.exists(path):
                  matched_path = storage.path(path)
                  if matched_path:
                      return matched_path
docs: Find a requested media file in an app's media fixtures locations.