Fixed potential security issue in subversion resource

Hi!
I found that my notification handler posts svn password in exception string to my notification handler, and this is kinda wrong and insecure. Of course I will fix actual handler, but people tend to do such mistakes, and it's better to be safe than sorry.
In order to mitigate this risk I extracted exception message string into separate method, which is overwritten in Subversion resource + added unit test for this case.
What do you think?