Getting source code following http://packaging.ubuntu.com fails with bzr: ERROR: Not a branch

# Context

Wishing to contribute to Ubuntu package.

# Operations done

Followed instructions in http://packaging.ubuntu.com/html/
especially http://packaging.ubuntu.com/html/getting-set-up.html

But at http://packaging.ubuntu.com/html/udd-intro.html problems start:

bzr branch ubuntu:kdetoys

bzr: ERROR: Not a branch: "bzr+ssh://bazaar.launchpad.net/+branch/ubuntu/kdetoys/".

Also http://packaging.ubuntu.com/html/udd-getting-the-source.html#branching

bzr init-repo tomboy

Shared repository with trees (format: 2a)
Location:
  shared repository: tomboy

cd tomboy

bzr branch ubuntu:tomboy tomboy.dev

bzr: ERROR: Not a branch: "bzr+ssh://bazaar.launchpad.net/+branch/ubuntu/tomboy/".

# Additional information

This might be specific to Xenial as observed on http://askubuntu.com/a/624762/68124

There
https://code.launchpad.net/ubuntu/+source/hello

Indeed there is no xenial branch on any of these
https://code.launchpad.net/ubuntu/+source/lightdm/+all-branches
https://code.launchpad.net/ubuntu/+source/tomboy/+all-branches
https://code.launchpad.net/ubuntu/+source/kdetoys/+all-branches

They have a Wily branch, though, but no Yaketty.

# Questions

(1) Does is mean that UDD is somehow lagging for recent releases?

(2) Practically, I ended up doing apt-get source (or even wget http://archive.ubuntu.com/ubuntu/pool/main/l/lightdm/$PKGVERSION ). Is there a way to contribute to Xenial and/or latest development packages using bzr?

Thank you for your attention.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: bzr 2.7.0-2ubuntu2
ProcVersionSignature: Ubuntu 4.4.0-34.53-generic 4.4.15
Uname: Linux 4.4.0-34-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: XFCE
Date: Wed Aug 17 12:22:29 2016
InstallationDate: Installed on 2016-07-05 (42 days ago)
InstallationMedia: Xubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
PackageArchitecture: all
SourcePackage: bzr
UpgradeStatus: No upgrade log present (probably fresh install)