text: from django.core.management.base import BaseCommand, CommandError
  from django.db import DEFAULT_DB_ALIAS, connections
  
  
  class Command(BaseCommand):
      help = ("Runs the command-line client for specified database, or the "
          "default database if none is provided.")
  
      requires_system_checks = False
  
      def add_arguments(self, parser):
          parser.add_argument('--database', action='store', dest='database',
              default=DEFAULT_DB_ALIAS, help='Nominates a database onto which to '
              'open a shell. Defaults to the "default" database.')
  
      def handle(self, **options):
          connection = connections[options['database']]
          try:
              connection.client.runshell()
          except OSError:
              # Note that we're assuming OSError means that the client program
              # isn't installed. There's a possibility OSError would be raised
              # for some other reason, in which case this error message would be
              # inaccurate. Still, this message catches the common case.
              raise CommandError('You appear not to have the %r program installed or on your path.' %
                  connection.client.executable_name)
  