ObjectStore must throw 404 when bucket does not exist (Commit 146)

Before the twisted rewrite of the objectstore, if a bucket did not exist, Bucket::__init__ would throw exception.NotFound(), and then the @catch_nova_exceptions annotation would wrap that as a 404. Now I think the exception is not being caught, and it is simply being thrown as a 500.

The problem is that e.g. euca-upload-bundle checks to see if a bucket should be created before upload by doing a GET on the bucket and looking for a 404. This logic now fails.

Essentially, the logic in catch_nova_exceptions has been lost. I presume NotAuthorized is thrown somewhere also, and should also be caught and wrapped.

def catch_nova_exceptions(target):
     # FIXME: find a way to wrap all handlers in the web.Application.__init__ ?
     def wrapper(*args, **kwargs):
         try:
             return target(*args, **kwargs)
         except exception.NotFound:
             raise web.HTTPError(404)
         except exception.NotAuthorized:
             raise web.HTTPError(403)

     return wrapper