Cask: no message to approve kext

On upgrading virtualbox with brew cask upgrade, it failed. I saw an alert to approve a system plugin (kext), but upon going to Security > General, nothing was there. Thinking I missed it, I tried brew cask reinstall virtualbox. But I just get this output:

 !  ~/v/f/d7d8  brew cask install virtualbox                                                  24.3s
==> Caveats
To install and/or use virtualbox you may need to enable its kernel extension in:
  System Preferences → Security & Privacy → General
For more information refer to vendor documentation or this Apple Technical Note:
  https://developer.apple.com/library/content/technotes/tn2459/_index.html

==> Satisfying dependencies
==> Downloading https://download.virtualbox.org/virtualbox/6.0.8/VirtualBox-6.0.8-130520-OSX.dmg
Already downloaded: /Users/kevin/Library/Caches/Homebrew/downloads/130d78b88001e8d144b4c39fedf0caa739515abf930f870f90f440eaf644ea8c--VirtualBox-6.0.8-130520-OSX.dmg
==> Verifying SHA-256 checksum for Cask 'virtualbox'.
==> Installing Cask virtualbox
==> Running installer for virtualbox; your password may be necessary.
==> Package installers may write to any location; options such as --appdir are ignored.
installer: Package name is Oracle VM VirtualBox
installer: Upgrading at base path /
installer: The upgrade failed (Installeraren stötte på ett fel som förhindrade installationen. Kontakta programtillverkaren och be om assistans.)
==> Purging files for version 6.0.8,130520 of Cask virtualbox
Error: Failure while executing; `/usr/bin/sudo -E -- env LOGNAME=kevin USER=kevin USERNAME=kevin /usr/sbin/installer -pkg /usr/local/Caskroom/virtualbox/6.0.8,130520/VirtualBox.pkg -target /` exited with 1. Here's the output:
installer: Package name is Oracle VM VirtualBox
installer: Upgrading at base path /
installer: The upgrade failed (Installeraren stötte på ett fel som förhindrade installationen. Kontakta programtillverkaren och be om assistans.)
Follow the instructions here:
  https://github.com/Homebrew/homebrew-cask#reporting-bugs
/usr/local/Homebrew/Library/Homebrew/system_command.rb:109:in `assert_success'
/usr/local/Homebrew/Library/Homebrew/system_command.rb:52:in `run!'
/usr/local/Homebrew/Library/Homebrew/system_command.rb:29:in `run'
/usr/local/Homebrew/Library/Homebrew/system_command.rb:33:in `run!'
/usr/local/Homebrew/Library/Homebrew/cask/artifact/pkg.rb:59:in `block in run_installer'
/usr/local/Homebrew/Library/Homebrew/cask/artifact/pkg.rb:65:in `with_choices_file'
/usr/local/Homebrew/Library/Homebrew/cask/artifact/pkg.rb:52:in `run_installer'
/usr/local/Homebrew/Library/Homebrew/cask/artifact/pkg.rb:34:in `install_phase'
/usr/local/Homebrew/Library/Homebrew/cask/installer.rb:214:in `block in install_artifacts'
/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/set.rb:674:in `each'
/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/set.rb:674:in `each'
/usr/local/Homebrew/Library/Homebrew/cask/installer.rb:205:in `install_artifacts'
/usr/local/Homebrew/Library/Homebrew/cask/installer.rb:103:in `install'
/usr/local/Homebrew/Library/Homebrew/cask/cmd/install.rb:23:in `block in run'
/usr/local/Homebrew/Library/Homebrew/cask/cmd/install.rb:16:in `each'
/usr/local/Homebrew/Library/Homebrew/cask/cmd/install.rb:16:in `run'
/usr/local/Homebrew/Library/Homebrew/cask/cmd/abstract_command.rb:36:in `run'
/usr/local/Homebrew/Library/Homebrew/cask/cmd.rb:93:in `run_command'
/usr/local/Homebrew/Library/Homebrew/cask/cmd.rb:159:in `run'
/usr/local/Homebrew/Library/Homebrew/cask/cmd.rb:124:in `run'
/usr/local/Homebrew/Library/Homebrew/cmd/cask.rb:9:in `cask'
/usr/local/Homebrew/Library/Homebrew/brew.rb:102:in `<main>'

Do the apple technical notes help? What does the install error say?

I only got the output I pasted. It seems like Homebrew Cask just cancels its request (or uninstalls the kext???) once it fails, so I can never confirm it.

What does this say?

Are you able to find it using this?

What happens if you remove and install instead of reinstall?