#16 PrivateAccessor failure messages are backwards

[Valerie Wagner]

When any of the methods in PrivateAccessor fail, the
message is "Could set...". It should instead read
"Could NOT set..." because we failed to set the field
or invoke the method.

[Nick Odaemus]

It seems that this was updated in the code (albeit only for one method) per the Revision History, but there hasn't been an update to the latest release.