Bump six from 1.11.0 to 1.12.0

Bumps [six](https://github.com/benjaminp/six) from 1.11.0 to 1.12.0.
- [Release notes](https://github.com/benjaminp/six/releases)
- [Changelog](https://github.com/benjaminp/six/blob/master/CHANGES)
- [Commits](benjaminp/six@1.11.0...1.12.0)

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

Author: dependabot-support

requirements.txt

@@ -9,5 +9,5 @@ py==1.7.0
 PyJWT==1.6.4
 pytest==3.9.3
 requests==2.20.0
-six==1.11.0
+six==1.12.0
 urllib3==1.25.2