docs: def clean(self):
          """
          Verifiy that the values entered into the two password fields
          match. Note that an error here will end up in
          ``non_field_errors()`` because it doesn't apply to a single
          field.
          """
          if 'dob_day' in self.cleaned_data and 'dob_month' in \
                  self.cleaned_data and 'dob_year' in self.cleaned_data:
                  try:
                      self._gen_dob()
                  except ValueError:
                      self._errors['dob_day'] = (_(\
                              "You provided an invalid date."),)
  
          if 'password1' in self.cleaned_data and 'password2' in \
                  self.cleaned_data:
              if self.cleaned_data['password1'] != \
                      self.cleaned_data['password2']:
                  raise forms.ValidationError(_(\
                          "The two password fields didn't match."))
  
          return self.cleaned_data