[FIX] event_sale: workaround for broken view.

Non-stored fields created with the new API are not converted to old
fields and added in `_columns` (and thus `_all_columns`). This forbid
them to be used in qweb views.
A fix will be commited in 8.0 to address this issue.

addons/event_sale/models/event.py

@@ -3,6 +3,7 @@
 from openerp import models, fields, api, _
 import openerp.addons.decimal_precision as dp
 from openerp.exceptions import Warning
+from openerp.osv import fields as old_fields
 
 
 class event_event(models.Model):
@@ -51,8 +52,6 @@ class event_ticket(models.Model):
         default=lambda self: self._default_product_id())
     registration_ids = fields.One2many('event.registration', 'event_ticket_id', 'Registrations')
     price = fields.Float('Price', digits=dp.get_precision('Product Price'))
-    price_reduce = fields.Float("Price Reduce", compute="_get_price_compute", store=False,
-                                digits=dp.get_precision('Product Price'))
     deadline = fields.Date("Sales End")
     is_expired = fields.Boolean('Is Expired', compute='_is_expired', store=True)
 
@@ -74,13 +73,32 @@ class event_ticket(models.Model):
         current_date = fields.Date.context_today(self.with_context({'tz': self.event_id.date_tz}))
         self.is_expired = self.deadline < current_date
 
+    # FIXME non-stored fields wont ends up in _columns (and thus _all_columns), which forbid them
+    #       to be used in qweb views. Waiting a fix, we create an old function field directly.
+    """
+    price_reduce = fields.Float("Price Reduce", compute="_get_price_reduce", store=False,
+                                digits=dp.get_precision('Product Price'))
     @api.one
     @api.depends('price', 'product_id.lst_price', 'product_id.price')
-    def _get_price_compute(self):
+    def _get_price_reduce(self):
         product = self.product_id
         discount = product.lst_price and (product.lst_price - product.price) / product.lst_price or 0.0
         self.price_reduce = (1.0 - discount) * self.price
+    """
+    def _get_price_reduce(self, cr, uid, ids, field_name, arg, context=None):
+        res = dict.fromkeys(ids, 0.0)
+        for ticket in self.browse(cr, uid, ids, context=context):
+            product = ticket.product_id
+            discount = product.lst_price and (product.lst_price - product.price) / product.lst_price or 0.0
+            res[ticket.id] = (1.0 - discount) * ticket.price
+        return res
 
+    _columns = {
+        'price_reduce': old_fields.function(_get_price_reduce, type='float', string='Price Reduce',
+                                            digits_compute=dp.get_precision('Product Price')),
+    }
+
+    # seats fields
     seats_max = fields.Integer('Maximum Available Seats', help="You can for each event define a maximum registration level. If you have too much registrations you are not able to confirm your event. (put 0 to ignore this rule )")
     seats_reserved = fields.Integer(string='Reserved Seats', compute='_compute_seats', store=True)
     seats_available = fields.Integer(string='Available Seats', compute='_compute_seats', store=True)