[Security] Bump requests from 2.18.4 to 2.20.1

[dependabot-preview]

Bumps requests from 2.18.4 to 2.20.1. This update includes security fixes.

Vulnerabilities fixed

Sourced from The GitHub Security Advisory Database.

Moderate severity vulnerability that affects requests
The Requests package through 2.19.1 before 2018-09-14 for Python sends an HTTP Authorization header to an http URI upon receiving a same-hostname https-to-http redirect, which makes it easier for remote attackers to discover credentials by sniffing the network.

Affected versions: <= 2.19.1

Changelog

Sourced from requests's changelog.

2.20.1 (2018-11-08)

Bugfixes

• Fixed bug with unintended Authorization header stripping for
  redirects using default ports (http/80, https/443).

2.20.0 (2018-10-18)

Bugfixes

• Content-Type header parsing is now case-insensitive (e.g.
  charset=utf8 v Charset=utf8).
• Fixed exception leak where certain redirect urls would raise
  uncaught urllib3 exceptions.
• Requests removes Authorization header from requests redirected
  from https to http on the same hostname. (CVE-2018-18074)
• should_bypass_proxies now handles URIs without hostnames (e.g.
  files).

Dependencies

• Requests now supports urllib3 v1.24.

Deprecations

• Requests has officially stopped support for Python 2.6.

2.19.1 (2018-06-14)

Bugfixes

• Fixed issue where status_codes.py's init function failed trying
  to append to a __doc__ value of None.

2.19.0 (2018-06-12)

Improvements

• Warn user about possible slowdown when using cryptography version
  < 1.3.4
• Check for invalid host in proxy URL, before forwarding request to
  adapter.
• Fragments are now properly maintained across redirects. (RFC7231
  7.1.2)
• Removed use of cgi module to expedite library load time.

... (truncated)

Commits

• 6cfbe1a v2.20.1
• c501ec9 Merge pull request #4853 from mainanick/master
• 045b706 Merge pull request #2 from requests/master
• ccbffe5 Incorrect ValueError Message
• eaab47f Merge pull request #4851 from requests/default_port_handling
• ea9436a proper handling for default ports in auth stripping
• 3a831be Merge pull request #1 from requests/master
• 7c812e9 Merge pull request #4839 from rabdill/patch-1
• 5fdc25b Reverting redirect examples back to intended URLs
• d2962f1 update maintainer contact info
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #52.