docs: def ReadArtifact(self, name, cursor=None):
      """Looks up an artifact with given name from the database."""
      cursor.execute("SELECT definition FROM artifacts WHERE name = %s", [name])
  
      row = cursor.fetchone()
      if row is None:
        raise db.UnknownArtifactError(name)
      else:
        return _RowToArtifact(row)