code: def post(self, *args, **kwargs):
          
          if self.steps.current not in self.steps.all:
              logger.warning("Current step '%s' is no longer valid, returning "
                             "to last valid step in the wizard.",
                             self.steps.current)
              return self.render_goto_step(self.steps.all[-1])
  
          # -- Duplicated code from upstream
          # Look for a wizard_goto_step element in the posted data which
          # contains a valid step name. If one was found, render the requested
          # form. (This makes stepping back a lot easier).
          wizard_goto_step = self.request.POST.get('wizard_goto_step', None)
          if wizard_goto_step and wizard_goto_step in self.get_form_list():
              return self.render_goto_step(wizard_goto_step)
  
          # Check if form was refreshed
          management_form = ManagementForm(self.request.POST, prefix=self.prefix)
          if not management_form.is_valid():
              raise SuspiciousOperation(_('ManagementForm data is missing or has been tampered with'))
  
          form_current_step = management_form.cleaned_data['current_step']
          if (form_current_step != self.steps.current and
                  self.storage.current_step is not None):
              # form refreshed, change current step
              self.storage.current_step = form_current_step
          # -- End duplicated code from upstream
  
          # This is different from the first check, as this checks
          # if the new step is available. See issue #65.
          if self.steps.current not in self.steps.all:
              logger.warning("Requested step '%s' is no longer valid, returning "
                             "to last valid step in the wizard.",
                             self.steps.current)
              return self.render_goto_step(self.steps.all[-1])
  
          return super(IdempotentSessionWizardView, self).post(*args, **kwargs)
docs: Check if the current step is still available. It might not be if
          conditions have changed.