Bump requests from 2.18.4 to 2.20.0

Bumps [requests](https://github.com/requests/requests) from 2.18.4 to 2.20.0.
- [Release notes](https://github.com/requests/requests/releases)
- [Changelog](https://github.com/psf/requests/blob/master/HISTORY.md)
- [Commits](psf/requests@v2.18.4...v2.20.0)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -7,7 +7,7 @@ pkginfo==1.4.2
 pypandoc==1.4
 python-dateutil==2.7.2
 PyYAML==3.12
-requests==2.18.4
+requests==2.20.0
 requests-toolbelt==0.8.0
 semantic-version==2.6.0
 six==1.11.0