docs: def get_obj(self, objpath, metahash, dst_path):
          """Get object from cache, write it to dst_path.
  
          Args:
            objpath: filename relative to buildroot
                     (example: mini-boot/blahblah/somefile.bin)
            metahash: metahash. See targets/base.py
            dst_path: Absolute path where the file should be written.
          Raises:
            CacheMiss: if the item is not in the cache
          """
          incachepath = self.path_in_cache(objpath, metahash)
          if not os.path.exists(incachepath):
              raise CacheMiss('%s not in cache.' % incachepath)
          else:
              log.debug('Cache hit! %s~%s', objpath, metahash.hexdigest())
              if not os.path.exists(os.path.dirname(dst_path)):
                  os.makedirs(os.path.dirname(dst_path))
              os.link(incachepath, dst_path)