Bump requests from 2.3.0 to 2.20.0

Bumps [requests](https://github.com/psf/requests) from 2.3.0 to 2.20.0.
- [Release notes](https://github.com/psf/requests/releases)
- [Changelog](https://github.com/psf/requests/blob/master/HISTORY.md)
- [Commits](psf/requests@v2.3.0...v2.20.0)

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

requirements.txt

@@ -15,6 +15,6 @@ pystache==0.5.4
 python3-openid==3.0.4
 raven==5.0.0
 requests-oauthlib==0.4.1
-requests==2.3.0
+requests==2.20.0
 six==1.7.2
 static==1.0.2