codereview.py: Fix crash on auth error handling.
codereview.py: Fix crash on auth error handling.

In recent Python versions .reason is a read-only property that simply gives you the msg value.

Fixes issue 4024

R=golang-dev, adg
CC=golang-dev
http://codereview.appspot.com/6545052

Committer: Shenghou Ma <b563c57947dc20eb81988e3e3c22786764c14ca8@gmail.com>

webfd/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,webfd/go-zh,rdp/rogerpack2005-golang,mhennings/marcohennings-go,bryanxu/go-zh,scirelli/scirelli-go,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,mhennings/marcohennings-go,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,d0f/go-zh,rflanagan/reginaldflanagan-project1,webfd/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,webfd/go-zh,rflanagan/reginaldflanagan-project1,d0f/go-zh,bryanxu/go-zh,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,bryanxu/go-zh,mhennings/marcohennings-go,bryanxu/go-zh,rdp/rogerpack2005-golang,webfd/go-zh,rflanagan/reginaldflanagan-project1,webfd/go-zh,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,mhennings/marcohennings-go,bryanxu/go-zh,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,bryanxu/go-zh,mhennings/marcohennings-go,d0f/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,scirelli/scirelli-go,bryanxu/go-zh,mhennings/marcohennings-go,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,rflanagan/reginaldflanagan-project1,rflanagan/reginaldflanagan-project1,webfd/go-zh,d0f/go-zh