client: don't swallow ResponseError inside open() _readhello() can generate meaningful ResponseError exceptions. However, open()'s exception handler swallows these, converting them into generic ServerErrors. Allow the original ResponseErrors to pass through.

#!/usr/bin/env python

import nose
from tests import with_hg

if __name__ == '__main__':
    nose.main(addplugins=[with_hg.WithHgPlugin()])