Distribution conflict: packages.dotdeb.org stable InRelease (expected stable but got jessie)?

Question

linux

I'm trying to start upgrading Debian 8 to Debian 9. In the source list, I indicated:

deb http://httpredir.debian.org/debian stretch main contrib non-free
deb http://httpredir.debian.org/debian stretch-updates main contrib non-free
deb http://security.debian.org/ stretch/updates main contrib non-free
deb http://packages.dotdeb.org stable all

after apt-get update I get:

Distribution conflict: packages.dotdeb.org stable InRelease (expected stable, but got jessie)

Why?
PS: vi does not highlight "stretch" when editing a source list, unlike "jessie". Why?

Answer 1

because the stable is jesse, the stretch is still in beta and should be released on may 27 if my memory doesn't deceive me.
and even then it seems to me that the release will be postponed