Remove warnings for unsupported features of SQLite table handler

There is no need to raise warnings as the API is called by ModelSQL and the
user has not control over it.

trytond/trytond/backend/sqlite/table.py

@@ -3,7 +3,6 @@
 
 import logging
 import re
-import warnings
 from weakref import WeakKeyDictionary
 
 from trytond.backend.table import (
@@ -184,7 +183,7 @@ class TableHandler(TableHandlerInterface):
         return base_type == db_type and same_size
 
     def db_default(self, column_name, value):
-        warnings.warn('Unable to set default on column with SQLite backend')
+        pass
 
     def add_column(self, column_name, sql_type, default=None, comment=''):
         database = Transaction().database
@@ -256,20 +255,15 @@ class TableHandler(TableHandlerInterface):
         self._update_definitions(columns=True)
 
     def add_fk(self, columns, reference, ref_columns=None, on_delete=None):
-        warnings.warn('Unable to add foreign key with SQLite backend')
+        pass
 
     def drop_fk(self, columns=None, ref_columns=None, table=None):
-        warnings.warn('Unable to drop foreign key with SQLite backend')
+        pass
 
     def not_null_action(self, column_name, action='add'):
         if not self.column_exist(column_name):
             return
-
-        if action == 'add':
-            warnings.warn('Unable to set not null with SQLite backend')
-        elif action == 'remove':
-            warnings.warn('Unable to remove not null with SQLite backend')
-        else:
+        if action not in {'add', 'remove'}:
             raise Exception('Not null action not supported!')
 
     def add_constraint(self, ident, constraint):
@@ -287,8 +281,6 @@ class TableHandler(TableHandlerInterface):
                     _escape_identifier(self.table_name),
                     ', '.join(map(str, constraint.columns)),
                     where))
-        else:
-            warnings.warn('Unable to add constraint with SQLite backend')
 
     def drop_constraint(self, ident, table=None):
         cursor = Transaction().connection.cursor()
@@ -312,8 +304,6 @@ class TableHandler(TableHandlerInterface):
                             _escape_identifier(self.table_name),
                             query),
                         params)
-                else:
-                    warnings.warn("Can not create index with parameters")
                 old.discard(name)
         for name in old:
             if name.startswith('idx_') or name.endswith('_index'):