trouble with debootstrap a ppc SPE build

hello debian folks, I need some help building debian using debootstrap.

I tried following the info under https://wiki.debian.org/PowerPCSPEPort
but I cannot get beyond the "Installing the port", debootstrap --keyring=...
gives me this error

# sudo debootstrap --keyring=/usr/share/keyrings/debian-ports-archive-keyring.gpg unstable rootfs-powerpcspe http://ftp.ports.debian.org/debian-ports/
    [sudo] password for xxx:
    I: Retrieving Release
    I: Retrieving Release.gpg
    I: Checking Release signature
    E: Release signed by unknown key (key id B4C86482705A2CE1)

And more info on my setup

I tried this on both debian 7 and debian 8 and I still have the issue unresolved.

# dpkg -L debian-ports-archive-keyring
/.
/usr
/usr/share
/usr/share/doc
/usr/share/doc/debian-ports-archive-keyring
/usr/share/doc/debian-ports-archive-keyring/changelog.gz
/usr/share/doc/debian-ports-archive-keyring/copyright
/usr/share/doc/debian-ports-archive-keyring/README
/usr/share/keyrings
/usr/share/keyrings/debian-ports-archive-keyring.gpg
/usr/share/keyrings/debian-ports-archive-keyring-removed.gpg

# sha1sum /usr/share/keyrings/debian-ports-archive-keyring.gpg
7ac085c220a7d71e759615ba9850e8c1ad1fa88f /usr/share/keyrings/debian-ports-archive-keyring.gpg

// And i added below lines to my /etc/apt/sources.list file as well.

deb http://ftp.ports.debian.org/debian-ports/ unstable main
deb http://ftp.ports.debian.org/debian-ports/ unreleased main
deb http://ftp.ports.debian.org/debian-ports/ experimental main

Please suggest what's the best way to resolve this.

Thanks

M J