'Add a terms of service field to a form description.
Arguments:
form_desc: A form description
Keyword Arguments:
required (bool): Whether this field is required; defaults to True'

def _add_terms_of_service_field(self, form_desc, required=True):

    terms_label = _(u'Terms    of    Service')
    terms_link = marketing_link('TOS')
    terms_text = _(u'Review    the    Terms    of    Service')
    label = _(u'I    agree    to    the    {platform_name}    {terms_of_service}').format(platform_name=configuration_helpers.get_value('PLATFORM_NAME', settings.PLATFORM_NAME), terms_of_service=terms_label)
    error_msg = _(u'You    must    agree    to    the    {platform_name}    {terms_of_service}').format(platform_name=configuration_helpers.get_value('PLATFORM_NAME', settings.PLATFORM_NAME), terms_of_service=terms_label)
    form_desc.add_field('terms_of_service', label=label, field_type='checkbox', default=False, required=required, error_messages={'required': error_msg}, supplementalLink=terms_link, supplementalText=terms_text)
