An attempt to invalidate the form in samples.py

samples.py

"""
Here you can create samples of your widgets by providing default parameters,
inserting them in a container widget, mixing them with other widgets, etc...
These samples will appear in the WidgetBrowser

See http://toscawidgets.org/documentation/WidgetBrowser for more information
"""

import tw2.core as twc
from tw2.forms.samples import DemoChildren

from tw2.bootstrap.widgets import *


class DemoHorizontalForm(HorizontalForm):
    legend = 'Hi, I\'m form!'
    title = TextField(validator=twc.Required)
    #priority = SingleSelectField(options=['', 'Normal', 'High'])
    description = TextArea
    buttons = [SubmitButton, ResetButton]
    
    def prepare(self):
        super(DemoHorizontalForm, self).prepare()

        original, DemoHorizontalForm.parent = DemoHorizontalForm.parent, None
        try:
            # This will fail
            DemoHorizontalForm.validate({})
        except:
            # Just so we know it failed.
            import traceback
            traceback.print_exc()
        finally:
            DemoHorizontalForm.parent = original

There is a much better version of this here:

https://github.com/moschlar/tw2.bootstrap/commit/73c1d12d3719e1679035bb898b36f091690d51e5