Adds fetchone to turn retrieval query

__init__.py

                 turn = db.execute(
                     'SELECT last_turn FROM station WHERE s_id=?',
                     (station_id,)
-                )
+                ).fetchone()
                 db.execute(
                     'INSERT INTO turno (cName, cEmail, turn, timeArrival, station)'
                     ' VALUES (?, ?, ?, ?)',