What’s new in Tornado 4.0.1

Aug 12, 2014

The build will now fall back to pure-python mode if the C extension fails to build for any reason (previously it would fall back for some errors but not others).
IOLoop.call_at and IOLoop.call_later now always return a timeout handle for use with IOLoop.remove_timeout.
If any callback of a PeriodicCallback or IOStream returns a Future, any error raised in that future will now be logged (similar to the behavior of IOLoop.add_callback).
Fixed an exception in client-side websocket connections when the connection is closed.
simple_httpclient once again correctly handles 204 status codes with no content-length header.
Fixed a regression in simple_httpclient that would result in timeouts for certain kinds of errors.