[merge] Ignore write errors when creating hashcache

[Aaron Bentley]

Aaron Bentley has voted +1 (conditional).
Status is now: Conditionally approved
Comment:
This looks reasonable to me.  But
- getattr will raise AttributeError unless you specify a default value.  I think you want getattr(tree, '_hashcache', None)

- I think you should do assertTrue(isinstance(the_hashcache, hashcache.HashCache)), because otherwise the test will appear to succeed.



For details, see: http://bundlebuggy.aaronbentley.com/request/%3C45881DA9.8020204%40arbash-meinel.com%3E