The purpose of this patch is to provide the original
session unpickle exception instead of KeyError
Since we have no corrupted sessions on the disk, the
Session KeyError is still appears.
KeyError appears if SessionFileStore can't unpickle
session while loading it from disk.
Session can't be unpickled only if it has objects, with
have buggy implemented unpickling feature.
Developer, who works under webkit, would like to fix
unpickling for his session.
So, match better for developer to see the original
exception instead of KeyError.
This patch was made on Webware0.8b1.