[MERGE][bug #125784] Don't suppress original errors when .unlock() fails

[Martin Pool]

Martin Pool has voted tweak.
Status is now: Conditionally approved
Comment:
+    except:
+        import sys

You already imported 'sys' at the top level; it's certainly already in 
memory.

As we mentioned in the bug it might have been nice to log or tell the 
user about any errors occurring while unlocking.

+class TestFastDecoratorActions(TestDecoratorActions):
+
+    _decorator_style = 'fast'
+
+
+class TestPrettyDecoratorActions(TestDecoratorActions):
+
+    _decorator_style = 'pretty'

(comment) I would kind of like if these could be written using the 
scenario multiplier code rather than subclassing, so that we can move 
towards consistently using that.  But I guess it can wait until someone 
goes to update all of them; it's not particularly cumbersome like this.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C484C10A9.9020108%40arbash-meinel.com%3E