BF: pass original exception into replace_surrogate_encode
BF: pass original exception into replace_surrogate_encode

Fixes my incorrect fix in #598

jeblair/GitPython,gitpython-developers/gitpython,breavo/GitPython,gitpython-developers/GitPython,gitpython-developers/GitPython,jeblair/GitPython,breavo/GitPython,gitpython-developers/gitpython