form: don't break on emails with empty parts in domain (#6796)

tests/test_widgets.py

@@ -234,6 +234,9 @@ def test_emailwidget():
     mock_form_submission(req, widget, {'test': 'foo@localhost@test'})
     assert widget.has_error()
 
+    widget = EmailWidget('test')
+    mock_form_submission(req, widget, {'test': 'foo@localhost..localdomain'})
+    assert widget.has_error()
 
 def test_date_widget():
     widget = DateWidget('test')

wcs/qommon/form.py

@@ -709,6 +709,11 @@ class EmailWidget(StringWidget):
             elif get_cfg('emails', {}).get('check_domain_with_dns', True):
                 # testing for domain existence
                 domain = self.value.split('@')[-1]
+                if [x for x in domain.split('.') if not x]:
+                    # empty parts in domain, ex: @example..net, or
+                    # @.example.net
+                    self.error = _('invalid address domain')
+                    return
                 if not type(domain) is unicode:
                     domain = unicode(domain, 'utf-8', 'ignore')
                 domain = domain.encode('idna')