Comment 2 for bug 1887638

On bionic, python3-httplib2 doesn't support proxies, but python-httplib2 does. (This was fixed in 0.11.0 - https://github.com/httplib2/httplib2/pull/90 - so focal should work fine.) The ubuntu-dev-tools backport switched pull-lp-source to python3. Reverting that (and making sure that the Python 2 python-ubuntutools package has enough supporting code, since at least some of this seems to have been removed) should avoid this problem.