(classic)ogra@pi3:~$ sudo apt-get -o "Debug::Acquire::gpgv=true" update 1>/dev/null
inside VerifyGetSigners
Preparing to exec:  /usr/bin/apt-key --quiet --readonly verify --status-fd 3 /tmp/apt.sig.f2zw6s /tmp/apt.data.G956gO
gpgv exited with status 111
Summary:
  Good: 
  Bad: 
  Worthless: 
  SoonWorthless: 
  NoPubKey: 
inside VerifyGetSigners
Preparing to exec:  /usr/bin/apt-key --quiet --readonly verify --status-fd 3 /tmp/apt.sig.G3mIlH /tmp/apt.data.QvH2xe
gpgv exited with status 111
Summary:
  Good: 
  Bad: 
  Worthless: 
  SoonWorthless: 
  NoPubKey: 
inside VerifyGetSigners
Preparing to exec:  /usr/bin/apt-key --quiet --readonly verify --status-fd 3 /tmp/apt.sig.oLz1GL /tmp/apt.data.opoTcn
gpgv exited with status 111
Summary:
  Good: 
  Bad: 
  Worthless: 
  SoonWorthless: 
  NoPubKey: 
inside VerifyGetSigners
Preparing to exec:  /usr/bin/apt-key --quiet --readonly verify --status-fd 3 /tmp/apt.sig.4lf8hR /tmp/apt.data.ErU5oy
gpgv exited with status 111
Summary:
  Good: 
  Bad: 
  Worthless: 
  SoonWorthless: 
  NoPubKey: 
W: GPG error: http://ports.ubuntu.com/ubuntu-ports xenial InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: The repository 'http://ports.ubuntu.com/ubuntu-ports xenial InRelease' is not signed.
W: GPG error: http://ports.ubuntu.com/ubuntu-ports xenial-updates InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: The repository 'http://ports.ubuntu.com/ubuntu-ports xenial-updates InRelease' is not signed.
W: GPG error: http://ports.ubuntu.com/ubuntu-ports xenial-backports InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: The repository 'http://ports.ubuntu.com/ubuntu-ports xenial-backports InRelease' is not signed.
W: GPG error: http://ports.ubuntu.com/ubuntu-ports xenial-security InRelease: Could not execute 'apt-key' to verify signature (is gnupg installed?)
W: The repository 'http://ports.ubuntu.com/ubuntu-ports xenial-security InRelease' is not signed.
(classic)ogra@pi3:~$