newt resolves to use the correct console package and the warning can be ignored.
runtimeco APT Repo Signing Key Change
If you have previously set up your computer to install newt or newtmgr Debian packages using apt-get prior to 1.1.0 release, the signing key for the runtimeco APT repo has changed. You will need to import the new public key again. You can do so as follows:
wget -qO - https://raw.githubusercontent.com/runtimeco/debian-mynewt/master/mynewt.gpg.key | sudo apt-key add -