Bump urllib3 from 1.23 to 1.24.2

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.23 to 1.24.2.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/master/CHANGES.rst)
- [Commits](urllib3/urllib3@1.23...1.24.2)

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

requirements.txt

@@ -21,5 +21,5 @@ PyYAML==3.13
 requests==2.19.1
 six==1.11.0
 typed-ast==1.1.0
-urllib3==1.23
+urllib3==1.24.2
 wrapt==1.10.11