[Pkg-shadow-devel] Cannot check out svn upstream source

[Charlie Brown]

I don't know if I do it right, but if I do
svn co svn://svn.debian.org/pkg-shadow/upstream
I get
svn: E210005: Unable to connect to a repository at URL
'svn://svn.debian.org/pkg-shadow/upstream'
svn: E210005: No repository found in 'svn://svn.debian.org/pkg-shadow/upstream'

How can I checkout the svn repo?
Sincerely,
王文鑫
Charlie