[Security] Bump requests from 2.19.1 to 2.20.0

Bumps [requests](https://github.com/requests/requests) from 2.19.1 to 2.20.0. **This update includes security fixes.**
- [Release notes](https://github.com/requests/requests/releases)
- [Changelog](https://github.com/requests/requests/blob/master/HISTORY.md)
- [Commits](psf/requests@v2.19.1...v2.20.0)

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

Author: dependabot-support

requirements.txt

@@ -45,7 +45,7 @@ python-jose[cryptography]==3.0.0
 pytz==2018.5
 PyYAML==3.13
 raven==6.9.0
-requests==2.19.1
+requests==2.20.0
 rsa==3.4.2
 s3transfer==0.1.13
 simplejson==3.16.0