[MERGE] check for None being returned for a hook

[Michael Hudson]

Hi,

After the discussion in the "[rfc] more control over activating fallback
repositories (aka what gets stacked on)" thread, it seemed that adding a
hook to inspect and interfere with the fallback location a branch
activates was the best option.  This merge directive does that.

Cheers,
mwh
-------------- next part --------------
A non-text attachment was scrubbed...
Name: stacking-altering-hook-3773.patch
Type: text/x-patch
Size: 8722 bytes
Desc: not available
Url : https://lists.ubuntu.com/archives/bazaar/attachments/20081009/59f8715b/attachment.bin