AttributeError: 'datetime.date' object has no attribute 'hour' when creating an option - group by hour - odoo-8

Question

I´m using odoo8 and want to create an option group by hour,
I know that I should not mess with core odoo code but it is just add to lines (I hope so), I check an "pivot by hour" module V10 and there are added the same two lines.
in addons\point_of_sale\report\pos_order_report_view.xml I added:
<filter string="Order Hour" context="{'group_by':'date:hour'}" help="Hour of order date"/>
and in server\openerp\modules.py in _read_group_process_groupby() method I added two lines:
def _read_group_process_groupby(self, gb, query, context):
split = gb.split(':')
field_type = self._fields[split[0]].type
gb_function = split[1] if len(split) == 2 else None
temporal = field_type in ('date', 'datetime')
tz_convert = field_type == 'datetime' and context.get('tz') in pytz.all_timezones
qualified_field = self._inherits_join_calc(self._table, split[0], query)
if temporal:
display_formats = {
'hour': 'HH:mm dd MMM yyyy', ###### added by me
'day': 'dd MMM yyyy',
'week': "'W'w YYYY",
'month': 'MMMM yyyy',
'quarter': 'QQQ yyyy',
'year': 'yyyy',
}
time_intervals = {
'hour': dateutil.relativedelta.relativedelta(hours=1), ###### added by me
'day': dateutil.relativedelta.relativedelta(days=1),
'week': datetime.timedelta(days=7),
'month': dateutil.relativedelta.relativedelta(months=1),
'quarter': dateutil.relativedelta.relativedelta(months=3),
'year': dateutil.relativedelta.relativedelta(years=1)
}
if tz_convert:
qualified_field = "timezone('%s', timezone('UTC',%s))" % (context.get('tz', 'UTC'),
qualified_field)
qualified_field = "date_trunc('%s', %s)" % (gb_function or 'month', qualified_field)
if field_type == 'boolean':
qualified_field = "coalesce(%s,false)" % qualified_field
return {
'field': split[0],
'groupby': gb,
'type': field_type,
'display_format': display_formats[gb_function or 'month'] if temporal else None,
'interval': time_intervals[gb_function or 'month'] if temporal else None,
'tz_convert': tz_convert,
'qualified_field': qualified_field
}
the whole traceback is the following:

Answer 1

Make sure that the types you pass to value are the same as the types you indexed on.
You pass the value that is the 'datetime.date' and this Return date object with the same year, month and day. Click Here
You can change it with to datetime.time()
Thanks

Answer 2

In models.py (with path: server/openerp) in _read_group_format_result method
.format_date(
need to be changed to
.format_datetime(