In OpenERP 7.0 Quotation, there is a button called "Send By Email" which when clicked opens the related template of sale order. From here you can send the Quotation to the partner. We can also specify the report to be attached with this mail in the template ie; in Settings > Email > Email Template, in tab "Advanced", there is a field called "Optional report to print and attach". You can specify the report to attach with the mail in this field. If you want to add the functionality to send the mail automatically from your button action, you can call function send_mail in email.template model which sends the mail for the record using the template specified as arguments.

self.pool.get('email.template').send_mail(cr, uid, template_id, record_id, force_send=True, context=context)

where template_id is the id of the template to use to send the mail, record_id is the id of the record in your case sale order id, force_send which when set true will send the mail instantaneously without queuing the mail in the email queue manager.