apt-get update difficulties with the key or signature 16126D3A3E5C1192

Question

when I run:

sudo apt-get update

I keep getting the error:

W: GPG error: http://archive.ubuntu.com trusty Release: The following signatures were invalid: BADSIG 16126D3A3E5C1192 Ubuntu Extras Archive Automatic Signing Key <ftpmaster@ubuntu.com>

I have tried all the remedies posted in other answers to this same question. For example:

1) sudo apt-get clean followed by mv /var/lib/apt/lists *somewhere else* and mkdir -p /var/lib/apt/lists/partial etc.

(2) I tried deleting the key 16126D3A3E5C1192. It didn't delete.

(3) I tried fetching a new key with

sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 16126D3A3E5C1192

I got this response:

Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --homedir /tmp/tmp.lZ8rAlRc2k --no-auto-check-trustdb --trust-model always --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyring /etc/apt/trusted.gpg.d/webupd8team-java.gpg --keyring /etc/apt/trusted.gpg.d/webupd8team-y-ppa-manager.gpg --recv-keys --keyserver keyserver.ubuntu.com 16126D3A3E5C1192
gpg: requesting key 3E5C1192 from hkp server keyserver.ubuntu.com
gpg: key 3E5C1192: "Ubuntu Extras Archive Automatic Signing Key <ftpmaster@ubuntu.com>" not changed
gpg: Total number processed: 1
gpg:              unchanged: 1

Apparently, the 'bad' key is unchanged!

So, back to square one when I run:

sudo apt-get update

I get the same error again. How do I fix this?

I'm running Ubuntu 14.04 on a VM on my Mac-book Pro retina 13-inch late 2013. The VM is in Oracle Virtual Box Version 5.0.20 r106931.
Thanks for the help.