Bump httplib2 from 0.12.0 to 0.19.0

Bumps [httplib2](https://github.com/httplib2/httplib2) from 0.12.0 to 0.19.0.
- [Release notes](https://github.com/httplib2/httplib2/releases)
- [Changelog](https://github.com/httplib2/httplib2/blob/master/CHANGELOG)
- [Commits](httplib2/httplib2@v0.12.0...v0.19.0)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]