Failed to open pull request: KeyError - 'github'

At the end of an otherwise successful run of
```
bloom-release map_store --track hydro --rosdistro hydro
```

I got the following error:

```
==> Generating pull request to distro file located at 'https://raw.github.com/ros/rosdistro/master/hydro/release.yaml'
Unified diff for the ROS distro file located at '/tmp/tmp7YK5IA/map_store-0.3.0-0.patch':
--- hydro/release.yaml
+++ hydro/release.yaml
@ -580,6 +580,11 @
       release: release/hydro/{package}/{version}
     url: https://github.com/ros-gbp/map_msgs-release.git
     version: 0.0.2-0
+  map_store:
+    tags:
+      release: release/hydro/{package}/{version}
Failed to open pull request: KeyError - 'github'
```

I saw this: https://github.com/ros-infrastructure/bloom/pull/160 and thought it might be related, but was not sure.

At the end of ~/.bloom_logs/bloom-release_2013-07-03_08.49.04.314965.log is this python stack trace:
```
[debug] Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/bloom/commands/release.py", line 724, in perform_release
    pull_request_url = open_pull_request(track, repository, distro)
  File "/usr/lib/pymodules/python2.7/bloom/commands/release.py", line 381, in open_pull_request
    updated_release_file = generate_ros_distro_diff(track, repository, distro)
  File "/usr/lib/pymodules/python2.7/bloom/commands/release.py", line 299, in generate_ros_distro_diff
    line = fmt('@{gf}' + line)
  File "/usr/lib/pymodules/python2.7/bloom/logging.py", line 355, in fmt
    msg = t.substitute(_ansi) + ansi('reset')
  File "/usr/lib/python2.7/string.py", line 172, in substitute
    return self.pattern.sub(convert, self.template)
  File "/usr/lib/python2.7/string.py", line 162, in convert
    val = mapping[named]
KeyError: 'github'

[error] Failed to open pull request: KeyError - 'github'
[error] SYS.EXIT
```

The only other thing I can think to add is that the release repo "url" that I entered was ```git@github.com:ros-gbp/map_store-release.git``` which is not technically a URL in the web sense, but it works for git and is more convenient because I have my ssh keys set up for github.