Consider multiple distribution files with REP-143

[wjwwood]

With REP-143 (ros-infrastructure/rep#87) there can be multiple distribution files, so bloom with try to use the new api in rosdistro (ros-infrastructure/rosdistro#45) to get a list of the distribution files and then take the last one. Otherwise it will fall back to the current rosdistro API, so this change is backwards compatible.

[wjwwood]

This works against the current rosdistro (repo and library).

@dirk-thomas for review.

[dirk-thomas]

lgtm

[tfoote]

+1, though once we're finished the transition we should use a versioned dependency and remove the backwards compatibility.

[dirk-thomas]

There is no strong reason to remove the REP 141 support anytime soon. rosdistro if supporting both formats too.

[tfoote]

I'm not talking about removing REP 141 support. I'm talking about removing the deprecated API support with the try catch logic. Once there's an released version of rosdistro which supports 141 and 143 there's no need for the try catch logic.

[dirk-thomas]

Yes, as soon as rosdistro is released the try/except can be removed in favor of a versioned dependency.

[wjwwood]

I created a ticket to track this: #334

[tfoote]

I've tested up to the pull-request stage and get this:

Traceback (most recent call last):
  File "/tmp/deploy_ros_buildfarm/venv/local/lib/python2.7/site-packages/bloom/commands/release.py", line 1058, in perform_release
    pull_request_url = open_pull_request(track, repository, distro, interactive)
  File "/tmp/deploy_ros_buildfarm/venv/local/lib/python2.7/site-packages/bloom/commands/release.py", line 665, in open_pull_request
    updated_distribution_file = generate_ros_distro_diff(track, repository, distro)
  File "/tmp/deploy_ros_buildfarm/venv/local/lib/python2.7/site-packages/bloom/commands/release.py", line 473, in generate_ros_distro_diff
    distro_file_name = get_relative_distribution_file_path(distro)
  File "/tmp/deploy_ros_buildfarm/venv/local/lib/python2.7/site-packages/bloom/commands/release.py", line 344, in get_relative_distribution_file_path
    distribution_file_url = urlparse(get_disitrbution_file_url(distro))
  File "/usr/lib/python2.7/urlparse.py", line 143, in urlparse
    tuple = urlsplit(url, scheme, allow_fragments)
  File "/usr/lib/python2.7/urlparse.py", line 176, in urlsplit
    cached = _parse_cache.get(key, None)
TypeError: unhashable type: 'list'

Failed to open pull request: TypeError - unhashable type: 'list'