[FIX] auth_ldap: fix authentication with special chars

encode the filter in utf-8

This prevents a UnicodeDecode error in python-ldap when the
filter contains non ascii characters.

opw-682783
closes odoo#10899
closes odoo#12710

addons/auth_ldap/users_ldap.py

@@ -102,7 +102,7 @@ def authenticate(self, conf, login, password):
             _logger.warning('Could not format LDAP filter. Your filter should contain one \'%s\'.')
             return False
         try:
-            results = self.query(conf, filter)
+            results = self.query(conf, filter.encode('utf-8'))
 
             # Get rid of (None, attrs) for searchResultReference replies
             results = [i for i in results if i[0]]