text: from __future__ import unicode_literals
  
  from django.core import management
  from django.core.management.base import CommandError
  
  from ...signals import perform_upgrade, post_upgrade, pre_upgrade
  
  
  class Command(management.BaseCommand):
      help = 'Performs the required steps after a version upgrade.'
  
      def handle(self, *args, **options):
          try:
              pre_upgrade.send(sender=self)
          except Exception as exception:
              raise CommandError(
                  'Error during pre_upgrade signal: %s, %s' % (
                      exception, type(exception)
                  )
              )
  
          management.call_command('installjavascript', interactive=False)
  
          try:
              perform_upgrade.send(sender=self)
          except Exception as exception:
              raise CommandError(
                  'Error during perform_upgrade signal; %s, %s' % (
                      exception, type(exception)
                  )
              )
  
          try:
              post_upgrade.send(sender=self)
          except Exception as exception:
              raise CommandError(
                  'Error during post_upgrade signal; %s, %s' % (
                      exception, type(exception)
                  )
              )
  