'Start the specified subsystem.
Args:
subsystem [string]: The name of the subsystem.
environ [dict]: If set, use these environment variables instead.
Returns:
The pid of the subsystem once running or EXTERNAL_PID if run elsewhere.'

def start_subsystem_if_local(self, subsystem, environ=None):

    host = self.__bindings.get('services.{system}.host'.format(system=subsystem))
    if (not is_local(host)):
        print 'Expecting    {subsystem}    to    be    on    external    host    {host}'.format(subsystem=subsystem, host=host)
        return self.EXTERNAL_PID
    return self.start_subsystem(subsystem, environ)
