Python 3 preparation: make fallback SysCallError an actual exception class. The code defines a fallback version of SysCallError when import of OpenSSL.SSL. But in Python 3, defining it as None and then using in "except" statements results in: TypeError: catching classes that do not inherit from BaseException is not allowed

from roundup.dist.command.build import build_message_files, check_manifest
from distutils.command.install_lib import install_lib as base

class install_lib(base):

    def run(self):
        check_manifest()
        build_message_files(self)
        base.run(self)