'Import applications and returns an app config for the given label.
Raise LookupError if no application exists with this label.'

def get_app_config(self, app_label):

    self.check_apps_ready()
    try:
        return self.app_configs[app_label]
    except KeyError:
        message = ("No    installed    app    with    label    '%s'." % app_label)
        for app_config in self.get_app_configs():
            if (app_config.name == app_label):
                message += ("    Did    you    mean    '%s'?" % app_config.label)
                break
        raise LookupError(message)
