add-apt-repository fails to add repository with no explanation; --massive-debug doesn't show debugging

Example run:

paulgear@peleg:~/.juju$ sudo apt-add-repository --massive-debug ppa:juju/stable
Cannot add PPA: 'ppa:juju/stable'.
Please check that the PPA name or format is correct.

This is on a network with egress filtering, and this appears to be the cause of the issue. Running wireshark shows that apt-add-repository is attempting a direct connection to launchpad.net on port 443.

Bugs as I see them:
1. apt-add-repository requires direct access to Internet
2. It is undocumented that apt-add-repository requires direct access to Internet
3. apt-add-repository offers no indication that it has attempted access to the Internet, nor why it failed
4. Adding --massive-debug offers no diagnostics at all
5. apt-add-repository doesn't honour the proxy settings in /etc/apt/apt.conf

Several users have reported this previously, but I couldn't find any matching bug. References:
- http://ubuntuforums.org/showthread.php?t=1599832
- http://askubuntu.com/questions/53146/how-do-i-get-add-apt-repository-to-work-through-a-proxy

Workaround that worked for me:
- add -E to sudo command to pass environment variables through, which then allows https_proxy to be honoured.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: software-properties-common 0.92.37.1
ProcVersionSignature: Ubuntu 3.13.0-35.62-generic 3.13.11.6
Uname: Linux 3.13.0-35-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.3
Architecture: amd64
CurrentDesktop: Unity
Date: Tue Sep 2 09:14:43 2014
PackageArchitecture: all
SourcePackage: software-properties
UpgradeStatus: No upgrade log present (probably fresh install)