[Twisted-Python] run queries in deffered, but not in transaction

[Mark Visser]

Matt Perry wrote:
> would swallow any exceptions thrown by deferred1 and continue on to 
> create deferred2.  If you did:
>
> d.addCallback(foo)
> d.addCallback(bar)
> d.addCallback(baz)
>
> then an exception in "foo" would break the whole callback chain.
You can also use addBoth(), which adds a callback and errback at the 
same time. Though I prefer the @inlineCallbacks semantics, since they 
produce much more readable code.

cheers,
-Mark