[Success!] [MERGE] document when to use custom exception classes (was Move RemoteRepository caching logic to CachedParentsProvider)

[Bundle Buggy]

This change has been merged.
Previous status: Approved

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C4941AF93.7000501%40sourcefrog.net%3E
Project: Bazaar