PARIS, Oct 20 (Reuters) - France could announce possible retaliatory measures in its fishing dispute with Britain by the end of the week, French government spokesman Gabriel Attal said on Wednesday. "We are positioning ourselves to take measures," Attal told a news conference following a meeting of the French Cabinet. Paris is infuriated by London"s refusal to grant what it considers the full number of licenses due to French fishing boats to operate in Britain"s territorial waters, and is threatening retaliatory measures.