Bump waitress from 1.1.0 to 1.4.0

[dependabot]

Bumps waitress from 1.1.0 to 1.4.0.

Changelog

Sourced from waitress's changelog.

1.4.0 (2019-12-20)

Bugfixes

- Waitress used to slam the door shut on HTTP pipelined requests without
  setting the ``Connection: close`` header as appropriate in the response. This
  is of course not very friendly. Waitress now explicitly sets the header when
  responding with an internally generated error such as 400 Bad Request or 500
  Internal Server Error to notify the remote client that it will be closing the
  connection after the response is sent.

- Waitress no longer allows any spaces to exist between the header field-name
  and the colon. While waitress did not strip the space and thereby was not
  vulnerable to any potential header field-name confusion, it should have sent
  back a 400 Bad Request. See [Pylons/waitress#273](https://github-redirect.dependabot.com/Pylons/waitress/issues/273)

Security Fixes

• Waitress implemented a "MAY" part of the RFC7230
  (https://tools.ietf.org/html/rfc7230#section-3.5) which states:

  Although the line terminator for the start-line and header fields is
  the sequence CRLF, a recipient MAY recognize a single LF as a line
  terminator and ignore any preceding CR.
  

  Unfortunately if a front-end server does not parse header fields with an LF
  the same way as it does those with a CRLF it can lead to the front-end and
  the back-end server parsing the same HTTP message in two different ways. This
  can lead to a potential for HTTP request smuggling/splitting whereby Waitress
  may see two requests while the front-end server only sees a single HTTP
  message.

  For more information I can highly recommend the blog post by ZeddYu Lu
  https://blog.zeddyu.info/2019/12/08/HTTP-Smuggling-en/

• Waitress used to treat LF the same as CRLF in Transfer-Encoding: chunked
  requests, while the maintainer doesn't believe this could lead to a security
  issue, this is no longer supported and all chunks are now validated to be
  properly framed with CRLF as required by RFC7230.

• Waitress now validates that the Transfer-Encoding header contains only
  transfer codes that it is able to decode. At the moment that includes the
  only valid header value being chunked.

  That means that if the following header is sent:

  Transfer-Encoding: gzip, chunked

... (truncated)

Commits

• f11093a Merge pull request from GHSA-g2xc-35jw-c63p
• e586be8 Version 1.4.0
• d1f283b Update CHANGES.txt and HISTORY.txt as appropriate
• 60f92b8 Allow end of chunk parser to be resumeable
• 8ecd8dc Improve validation of Transfer-Encoding
• 575994c Upon receiving invalid Content-Length bail
• 804e313 Disallow BWS in header field-names
• fb08ecf Properly enforce max_request_header_size
• 8eba394 Remove support for non CRLF line endings
• 7ff1e6b Make sure all errors have a code/reason
• Additional commits viewable in compare view

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[dependabot]

A newer version of waitress exists, but since this PR has been edited by someone other than Dependabot I haven't updated it. You'll get a PR for the updated version as normal once this PR is merged.