npm5からnpm cache cleanだけではダメらしい gulpに不具合があり、npm cache cleanしようとするとうまくいかない。 $ npm cache clean npm ERR! As of npm@5, the npm cache self-heals from corruption issues npm ERR! by treating integrity mismatches as cache misses. As a result, npm ERR! data extracted from the cache is guaranteed to be valid. If you npm ERR! want to make sure everything is consistent, use `npm cache verify` npm ERR! instead.