Create marker table if it doesn't exist.

        Using a separate connection since the transaction might have to be reset.

def create_marker_table(self):
        """
        Create marker table if it doesn't exist.

        Using a separate connection since the transaction might have to be reset.
        """
        connection = self.connect()
        connection.autocommit = True
        cursor = connection.cursor()
        if self.use_db_timestamps:
            sql = """ CREATE TABLE {marker_table} (
                      update_id TEXT PRIMARY KEY,
                      target_table TEXT,
                      inserted TIMESTAMP DEFAULT NOW())
                  """.format(marker_table=self.marker_table)
        else:
            sql = """ CREATE TABLE {marker_table} (
                      update_id TEXT PRIMARY KEY,
                      target_table TEXT,
                      inserted TIMESTAMP);
                  """.format(marker_table=self.marker_table)

        try:
            cursor.execute(sql)
        except psycopg2.ProgrammingError as e:
            if e.pgcode == psycopg2.errorcodes.DUPLICATE_TABLE:
                pass
            else:
                raise
        connection.close()