Comment 2 for bug 1338769

I gave this a test. Here's the process. Everything appears to be good according to the test case.

1. proposed added but disabled: grep proposed /etc/apt/sources.list

# proposed
#deb http://archive.ubuntu.com/ubuntu/ trusty-proposed restricted main multiverse universe

2. pull-lp-source docker.io

dpkg-source: info: extracting docker.io in docker.io-1.0.1~dfsg1
dpkg-source: info: unpacking docker.io_1.0.1~dfsg1.orig.tar.gz
dpkg-source: info: unpacking docker.io_1.0.1~dfsg1-0ubuntu1.debian.tar.xz
dpkg-source: info: applying upstream-patched-archive-tar.patch
dpkg-source: info: applying change-system-unit-env-file.patch
dpkg-source: info: applying enable-non-amd64-arches.patch
pull-lp-source: Downloading docker.io version 1.0.1~dfsg1-0ubuntu1

3. cd docker.io-* && pwd
/home/rharper/work/docker_sru/1338769/docker.io-1.0.1~dfsg1

4. apt-get build-deb docker.io
(kriek) docker.io-1.0.1~dfsg1 % sudo apt-get build-dep docker.io
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
  btrfs-tools debhelper dh-apparmor dh-golang dh-systemd golang
  golang-context-dev golang-doc golang-go golang-go-linux-amd64
  golang-go.net-dev golang-gocapability-dev golang-gosqlite-dev golang-mux-dev
  golang-pty-dev golang-src libapparmor-dev libdevmapper-dev liblzo2-2
  libpcre3-dev libselinux1-dev libsepol1-dev libsqlite0 libsqlite0-dev
  libsqlite3-dev libudev-dev po-debconf
0 upgraded, 27 newly installed, 0 to remove and 0 not upgraded.
Need to get 30.2 MB/30.2 MB of archives.
After this operation, 187 MB of additional disk space will be used.
Do you want to continue? [Y/n] y

5. dpkg-checkbuilddeps debian/control 2>&1 | grep gocapability
dpkg-checkbuilddeps: Unmet build dependencies: golang-context-dev (>= 0.0~git20140520~) golang-dbus-dev (>= 1~) golang-go-systemd-dev (>= 2~) golang-gocapability-dev (>= 0.0~git20140516~) golang-mux-dev (>= 0.0~git20140505~) golang-pty-dev (>= 0.0~git20140315.1.67e2db2-1~)

6. enable proposed && apt-get install golang-gocapability-dev
(kriek) docker.io-1.0.1~dfsg1 % sudo apt-get install golang-gocapability-dev/trusty-proposed
Reading package lists... Done
Building dependency tree
Reading state information... Done
Selected version '0.0~git20140516-1~ubuntu0.14.04.1' (Ubuntu:14.04/trusty-proposed [all]) for 'golang-gocapability-dev'
The following packages will be upgraded:
  golang-gocapability-dev
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 9,470 B of archives.
After this operation, 1,024 B of additional disk space will be used.
0% [Working]Failed to exec method /usr/share/squid-deb-proxy-client/apt-avahi-discover
Get:1 http://archive.ubuntu.com/ubuntu/ trusty-proposed/universe golang-gocapability-dev all 0.0~git20140516-1~ubuntu0.14.04.1 [9,470 B]
Fetched 9,470 B in 0s (34.5 kB/s)
sh: 0: getcwd() failed: No such file or directory
sh: 0: getcwd() failed: No such file or directory
sh: 0: getcwd() failed: No such file or directory
(Reading database ... 108027 files and directories currently installed.)
Preparing to unpack .../golang-gocapability-dev_0.0~git20140516-1~ubuntu0.14.04.1_all.deb ...
Unpacking golang-gocapability-dev (0.0~git20140516-1~ubuntu0.14.04.1) over (0.0~git20130208-1) ...
Setting up golang-gocapability-dev (0.0~git20140516-1~ubuntu0.14.04.1) ...

7. recheck (5), dpkg-checkbuilddeps debian/control 2>&1 | grep gocapability; echo $?
1