Prevent assign unknown attributes on Model

by adding __slots__ on PoolMeta

issue8567
review254091002

account.py

@@ -50,6 +50,7 @@ def inactive_records(func):
 def TypeMixin(template=False):
 
     class Mixin:
+        __slots__ = ()
         name = fields.Char('Name', required=True)
 
         statement = fields.Selection([
@@ -418,6 +419,7 @@ class OpenType(Wizard):
 def AccountMixin(template=False):
 
     class Mixin:
+        __slots__ = ()
         name = fields.Char('Name', required=True, select=True)
         code = fields.Char('Code', select=True)
 

move_template.py

@@ -362,4 +362,5 @@ class CreateMoveTemplate(ModelView):
 
 class CreateMoveKeywords(ModelView):
     'Create Move from Template'
+    __no_slots__ = True
     __name__ = 'account.move.template.create.keywords'

tax.py

@@ -1074,6 +1074,7 @@ _TaxableLine = namedtuple('_TaxableLine', ('taxes', 'unit_price', 'quantity'))
 
 
 class TaxableMixin(object):
+    __slots__ = ()
 
     @property
     def taxable_lines(self):