Retrieves metadata for a specific photo.

        flickr:(credsfile),photo,(photo_id)

def photo(self, args):
        """
        Retrieves metadata for a specific photo.

        flickr:(credsfile),photo,(photo_id)
        """
        rsp = self._load_rsp(self.flickr.photos_getInfo(photo_id=args[0]))
        p = rsp['photo']
        yield self._prep(p)