Clear queues at ingest startup.

Clear queues at ingest startup.

Bundles seem to get stuck when the job entries are locked and the ingest
process dies, such as happens when charm attributes are set or the charm gets
updated.

To avoid having the queues littered with items that never go away, which is
disconcerting to the casual viewer of /heartbeat, this branch introduces a new
--clear option to the queueing process which is used by the worker on the
first invocation

This branch also addresses a few other issues by being more defensive in the
face of charms and bundles that are non-standard in a number of ways.

* Handle the lack of 'bundles.yaml' gracefully.

* Handle SVG files with float placement values.

* Handle charms with no files.  The only instance I've seen of this occurring
  is with a charm that is private in Launchpad, so I cannot assess how it
  happens.

https://code.launchpad.net/~bac/charmworld/fix-ingestion-errors/+merge/201945

(do not edit description out of merge proposal)

[bac, 2014-01-16 15:21:43]

Please take a look.

[bac, 2014-01-16 15:41:15]

QA: 

In one terminal 
% make run

Open your browser and go to /heartbeat.  Verify there are no charms or bundles
in the queue.

In another terminal run
% bin/enqueue --prefix=~bac

Each time you run it, the number of queued charms and bundles should increase by
1 and 5.

Run 
% bin/enqueue --prefix=~bac --clear

and witness that the queues are cleared and then set to 1 and 5.

You can queue up a bunch of bundles and run
% bin/ingest-queued --prefix=~bac --clear

to see the queues get cleared.

[rharding, 2014-01-16 17:34:34]

LGTM with a couple of comments. QA starting.

https://codereview.appspot.com/51010046/diff/1/charmworld/jobs/ingest.py
File charmworld/jobs/ingest.py (right):

https://codereview.appspot.com/51010046/diff/1/charmworld/jobs/ingest.py#newc...
charmworld/jobs/ingest.py:411: self.log.error('No deployer config file found for
{}.'.format(
since we're looking for bundles.yaml, should we spell that out here for easier
debugging vs 'deployer file'?

https://codereview.appspot.com/51010046/diff/1/charmworld/models.py
File charmworld/models.py (right):

https://codereview.appspot.com/51010046/diff/1/charmworld/models.py#newcode119
charmworld/models.py:119: if float(width) <= 0 or float(height) <= 0:
is there a matching test to make sure it supports float values?

https://codereview.appspot.com/51010046/diff/1/charmworld/tests/test_models.py
File charmworld/tests/test_models.py (right):

https://codereview.appspot.com/51010046/diff/1/charmworld/tests/test_models.p...
charmworld/tests/test_models.py:2711: file_content = '<svg width="10.7"
height="11.2"></svg>'
yep, never mind. Good stuff!

[rharding, 2014-01-16 17:38:08]

QA ok