[Security] Bump requests from 2.7.0 to 2.20.0

[dependabot-preview]

Bumps requests from 2.7.0 to 2.20.0. 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.

2.20.0 (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.
• Added support for SHA-256 and SHA-512 digest auth algorithms.
• Minor performance improvement to Request.content.
• Migrate to using collections.abc for 3.7 compatibility.

Bugfixes

• Parsing empty Link headers with parse_header_links() no longer
  return one bogus entry.

... (truncated)

Commits

• bd84045 v2.20.0
• 7fd9267 remove final remnants from 2.6
• 6ae8a21 Add myself to AUTHORS
• 89ab030 Use comprehensions whenever possible
• 2c6a842 Merge pull request #4827 from webmaven/patch-1
• 30be889 CVE URLs update: www sub-subdomain no longer valid
• a6cd380 Merge pull request #4765 from requests/encapsulate_urllib3_exc
• bbdbcc8 wrap url parsing exceptions from urllib3's PoolManager
• ff0c325 Merge pull request #4805 from jdufresne/https
• b0ad249 Prefer https:// for URLs throughout project
• Additional commits viewable in compare view

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