This is what I get after deleting the source.list.d after reading a forum online about my update error. Initially it gave --add key...-- error.
$ sudo apt-get update
Reading package lists... Done
W: Unable to read /etc/apt/sources.list.d/ - DirectoryExists (2: No such file or directory)
W: Unable to read /etc/apt/sources.list - RealFileExists (2: No such file or directory)
sources.list.d
directory by runningsudo mkdir /etc/apt/sources.list.d
. – BeastOfCaerbannog Sep 24 '19 at 15:52