As per 28.0 and 28.1, apt-get upgrade has a bunch of errors at the end:
nvidia@tegra-ubuntu:~$ sudo apt-get update
...........................
Get:30 http://ports.ubuntu.com/ubuntu-ports xenial-security/main arm64 Packages [357 kB]
Get:31 http://ports.ubuntu.com/ubuntu-ports xenial-security/main arm64 DEP-11 Metadata [67.7 kB]
Get:32 http://ports.ubuntu.com/ubuntu-ports xenial-security/main DEP-11 64x64 Icons [68.1 kB]
Get:33 http://ports.ubuntu.com/ubuntu-ports xenial-security/universe arm64 Packages [294 kB]
Get:34 http://ports.ubuntu.com/ubuntu-ports xenial-security/universe arm64 DEP-11 Metadata [107 kB]
Get:35 http://ports.ubuntu.com/ubuntu-ports xenial-security/universe DEP-11 64x64 Icons [147 kB]
Fetched 3,946 kB in 3s (1,029 kB/s)
Reading package lists... Done
W: GPG error: file:/var/cuda-repo-9-0-local Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F60F4B3D7FA2AF80
W: The repository 'file:/var/cuda-repo-9-0-local Release' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: file:/var/nv-tensorrt-repo-ga-cuda9.0-trt3.0.4-20180208 Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F60F4B3D7FA2AF80
W: The repository 'file:/var/nv-tensorrt-repo-ga-cuda9.0-trt3.0.4-20180208 Release' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
How do I get rid of these?