old_contents: from django.forms import ModelForm
  from django import forms
  from django.forms.widgets import TextInput
  from django.core.urlresolvers import reverse
  from django.utils.translation import ugettext as _
  from braces.forms import UserKwargModelFormMixin
  from crispy_forms.helper import FormHelper
  from crispy_forms.layout import Submit
  from constance import config
  from .models import Signature
  
  
  class TelephoneInput(TextInput):
      input_type = 'tel'
  
  
  class SignatureForm(UserKwargModelFormMixin, ModelForm):
      giodo = forms.BooleanField(widget=forms.CheckboxInput(), required=True)
  
      def __init__(self, *args, **kwargs):
          super(SignatureForm, self).__init__(*args, **kwargs)
          self.helper = FormHelper()
          self.helper.form_action = reverse('petition:create')
          self.helper.form_method = 'post'
          self.helper.add_input(Submit('submit', _('Sign'), css_class="btn-lg btn-block"))
          self.fields['telephone'].widget = TelephoneInput()
          self.fields['newsletter'].label = config.NEWSLETTER_TEXT
          self.fields['giodo'].label = config.AGGREMENT_TEXT
  
      class Meta:
          model = Signature
          fields = ['first_name', 'second_name', 'email', 'city', 'telephone', 'giodo', 'newsletter']
  
new_contents: from django.forms import ModelForm
  from django import forms
  from django.forms.widgets import TextInput
  from django.core.urlresolvers import reverse
  from django.utils.translation import ugettext as _
  from braces.forms import UserKwargModelFormMixin
  from crispy_forms.helper import FormHelper
  from crispy_forms.layout import Submit
  from constance import config
  from .models import Signature
  
  
  class TelephoneInput(TextInput):
      input_type = 'tel'
  
  
  class SignatureForm(UserKwargModelFormMixin, ModelForm):
      giodo = forms.BooleanField(widget=forms.CheckboxInput(), required=True)
  
      def __init__(self, *args, **kwargs):
          super(SignatureForm, self).__init__(*args, **kwargs)
          self.helper = FormHelper()
          self.helper.form_action = reverse('petition:create')
          self.helper.form_method = 'post'
          self.helper.add_input(Submit('submit', _('Sign'), css_class="btn-sign btn-lg btn-block"))
          self.fields['telephone'].widget = TelephoneInput()
          self.fields['newsletter'].label = config.NEWSLETTER_TEXT
          self.fields['giodo'].label = config.AGGREMENT_TEXT
  
      class Meta:
          model = Signature
          fields = ['first_name', 'second_name', 'email', 'city', 'telephone', 'giodo', 'newsletter']
  
subject: Add a class for sign button