[Security] Bump requests from 2.18.4 to 2.21.0

[dependabot-preview]

Bumps requests from 2.18.4 to 2.21.0. 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.

2.21.0 (2018-12-10)

Dependencies

• Requests now supports idna v2.8.

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

... (truncated)

Commits

• 5a1e738 v2.21.0
• 8761e97 Bumped maximum version of idna
• abe950c Revert "Set up Azure Pipelines for Linux and Windows"
• c35f342 Merge pull request #4898 from requests/revert_azure
• 0dd4752 revert azure pipeline changes
• 57d7284 Merge pull request #4874 from kaylangan/patch-1
• fc9dfac Add build badge for Azure Pipelines
• bc3eddc Delete settings.json
• d911f27 Delete install.ps1
• 3da2f10 Delete .travis.yml
• Additional commits viewable in compare view

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[leplatrem]

@dependabot rebase