DeprecationWarning in Python 2.7

[wrygiel]

Hi! I just got this warning. Warning's not an error, but I think it's something to be fixed anyway :)

  (...)
    rootelem = xmldsig_obj.verify(x509_cert=pem_cert)
  File "D:\...\site-packages\signxml\__init__.py", line 631, in verify
    lib, func, reason = e.message[0]
DeprecationWarning: BaseException.message has been deprecated as of Python 2.6

https://github.com/kislyuk/signxml/blob/6079430a80ce10d903ea044f609ae82dc1b0d8b4/signxml/__init__.py#L631