exceptions.KeyError: u'subarches' when syncing uploaded image from region to cluster

[Jason Hobbs]

This is at version 1.7.0~beta2+bzr2847-0ubuntu1~ppa1.

After uploading a CentOS image via the API, I get an error in pserv.log:

2014-08-30 18:16:06+0000 [-] Unhandled error in Deferred:
2014-08-30 18:16:06+0000 [-] Unhandled Error
        Traceback (most recent call last):
          File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 423, in errback
            self._startRunCallbacks(fail)
          File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 490, in _startRunCallbacks
            self._runCallbacks()
          File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 577, in _runCallbacks
            current.result = callback(current.result, *args, **kw)
          File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1155, in gotResult
            _inlineCallbacks(r, g, deferred)
        --- <exception caught here> ---
          File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1097, in _inlineCallbacks
            result = result.throwExceptionIntoGenerator(g)
          File "/usr/lib/python2.7/dist-packages/twisted/python/failure.py", line 389, in throwExceptionIntoGenerator
            return g.throw(self.type, self.value, self.tb)
          File "/usr/lib/python2.7/dist-packages/provisioningserver/rpc/boot_images.py", line 53, in import_boot_images
            yield deferToThread(_run_import, sources)
          File "/usr/lib/python2.7/dist-packages/twisted/python/threadpool.py", line 191, in _worker
            result = context.call(ctx, function, *args, **kwargs)
          File "/usr/lib/python2.7/dist-packages/twisted/python/context.py", line 118, in callWithContext
            return self.currentContext().callWithContext(ctx, func, *args, **kw)
          File "/usr/lib/python2.7/dist-packages/twisted/python/context.py", line 81, in callWithContext
            return func(*args,**kw)
          File "/usr/lib/python2.7/dist-packages/provisioningserver/utils/twisted.py", line 143, in wrapper
            return func(*args, **kwargs)
          File "/usr/lib/python2.7/dist-packages/provisioningserver/rpc/boot_images.py", line 47, in _run_import
            boot_resources.import_images(sources)
          File "/usr/lib/python2.7/dist-packages/provisioningserver/import_images/boot_resources.py", line 234, in import_images
            image_descriptions = download_all_image_descriptions(sources)
          File "/usr/lib/python2.7/dist-packages/provisioningserver/import_images/download_descriptions.py", line 196, in download_all_image_descriptions
            source['url'], keyring=source.get('keyring', None))
          File "/usr/lib/python2.7/dist-packages/provisioningserver/import_images/download_descriptions.py", line 182, in download_image_descriptions
            dumper.sync(reader, rpath)
          File "/usr/lib/python2.7/dist-packages/simplestreams/mirrors/__init__.py", line 88, in sync
            return self.sync_index(reader, path, data, content)
          File "/usr/lib/python2.7/dist-packages/simplestreams/mirrors/__init__.py", line 240, in sync_index
            self.sync(reader, path=epath)
          File "/usr/lib/python2.7/dist-packages/simplestreams/mirrors/__init__.py", line 86, in sync
            return self.sync_products(reader, path, data, content)
          File "/usr/lib/python2.7/dist-packages/simplestreams/mirrors/__init__.py", line 318, in sync_products
            self.insert_item(item, src, target, pgree, ipath_cs)
          File "/usr/lib/python2.7/dist-packages/provisioningserver/import_images/download_descriptions.py", line 82, in insert_item
            arch, subarches = item['arch'], item['subarches']
        exceptions.KeyError: u'subarches'

My download.json @ http://paste.ubuntu.com/8189810/ shows no subarches field for the centos product.