code: def _get_image_stream_info_for_build_request(self, build_request):
          
          image_stream = None
          image_stream_tag_name = None
  
          if build_request.has_ist_trigger():
              image_stream_tag_id = build_request.trigger_imagestreamtag
              image_stream_id, image_stream_tag_name = image_stream_tag_id.split(':')
  
              try:
                  image_stream = self.get_image_stream(image_stream_id).json()
              except OsbsResponseException as x:
                  if x.status_code != 404:
                      raise
  
              if image_stream:
                  try:
                      self.get_image_stream_tag(image_stream_tag_id).json()
                  except OsbsResponseException as x:
                      if x.status_code != 404:
                          raise
  
          return image_stream, image_stream_tag_name
docs: Return ImageStream, and ImageStreamTag name for base_image of build_request
  
          If build_request is not auto instantiated, objects are not fetched
          and None, None is returned.