Update func_noerror_forms_py33 with test for #284

Include `Form` class to test that assigning a specific widget doesn't throw an error, as mentioned in #284.

Author: uy-rrodriguez

pylint_django/tests/input/func_noerror_forms_py33.py

@@ -31,3 +31,12 @@ class Meta:
 class TestModelFormSubclass(forms.ModelForm):
     class Meta:
         pass
+
+
+class TestFormWidgetAssignment(forms.Form):
+
+    multi_field = forms.MultipleChoiceField(choices=[('1', 'First'), ('2', 'Second')])
+
+    class Meta:
+        widgets = {}
+        widgets['multi_field'] = forms.CheckboxSelectMultiple