Return the map data.

def data(self, run_config):
    """Return the map data."""
    try:
      return run_config.map_data(self.path)
    except (IOError, OSError) as e:  # Catch both for python 2/3 compatibility.
      if self.download and hasattr(e, "filename"):
        logging.error("Error reading map '%s' from: %s", self.name, e.filename)
        logging.error("Download the map from: %s", self.download)
      raise