Bug: if a Nijie login failed with a 429 Too Many Requests error, the
error would get cached, so when we retried the request, we would just
get our own cached response back every time. The 429 error would
eventually be passed up to the Nijie strategy, which caused random
methods to fail because they couldn't get the html page.
Fix: add the `retriable` feature *after* the `cache` feature so that
retries don't go through the cache. This is a hack. We want retries to
go at the bottom of the stack, below caching, but we can't enforce this
ordering.
