Change the way transaction is initiated as readonly support was introduced in version 2.4
# -*- coding: UTF-8 -*-
'''
    nereid.backend

    Backed - Tryton specific features

    :copyright: (c) 2010-2012 by Openlabs Technologies & Consulting (P) Ltd.
    :license: GPLv3, see LICENSE for more details
'''
class TransactionManager(object):

    def __init__(self, database_name, user, context=None):
        self.database_name = database_name
        self.user = user
        self.context = context if context is not None else {}

    def __enter__(self):
        from trytond.transaction import Transaction
        Transaction().start(
            self.database_name, self.user,
            readonly=False, context=self.context.copy()
        )
        return Transaction()

    def __exit__(self, type, value, traceback):
        from trytond.transaction import Transaction
        Transaction().stop()

# -*- coding: UTF-8 -*-
'''
    nereid.backend

    Backed - Tryton specific features

    :copyright: (c) 2010-2012 by Openlabs Technologies & Consulting (P) Ltd.
    :license: GPLv3, see LICENSE for more details
'''
class TransactionManager(object):

    def __init__(self, database_name, user, context=None):
        self.database_name = database_name
        self.user = user
        self.context = context if context is not None else {}

    def __enter__(self):
        from trytond.transaction import Transaction
        Transaction().start(self.database_name, self.user, self.context.copy())
        return Transaction()

    def __exit__(self, type, value, traceback):
        from trytond.transaction import Transaction
        Transaction().stop()
