1 package can be upgraded. Run ‘apt list --upgradable’ to see it. W: gpgv:/var/lib/apt/lists/ppa.launchpad.net_flexiondotorg_hal-flash_ubuntu_dists_xenial_InRelease: The repository is insufficiently signed by key 824A27DD09DEDA33BF7835962EA8F35793D8809A (weak digest) W: gpgv:/var/lib/apt/lists/partial/ppa.launchpad.net_ubuntu-mate-dev_welcome_ubuntu_dists_xenial_InRelease: The repository is insufficiently signed by key 709A860A600B9A61FEF5346AFB01CC26162506E7 (weak digest)
Debian have made some changes to signature verification, in which Ubuntu will be following suit. So some repositories may temporarily show this warning.