MacDown fails to install, Permission denied to copy _CodeSignature

[czeluff]

General troubleshooting steps

• [ c] I understand that if I ignore these instructions, my issue may be closed without review.
• [c ] I have retried my command with --force.
• [ c] I ran brew update-reset && brew update and retried my command.
• [ c] I ran brew doctor, fixed as many issues as possible and retried my command.
• [ c] I have checked the instructions for reporting bugs.
• [ c] I made doubly sure this is not a checksum does not match error.

Description of issue

Download of MacDown completes, but fails to install, citing a permissions issue.

Command that failed

brew cask install macdown

Output of command with --force --verbose --debug

==> Cask::Installer#install
==> Printing caveats
==> Cask::Installer#fetch
==> Downloading
==> Downloading https://github.com/MacDownApp/macdown/releases/download
/usr/bin/curl --disable --globoff --show-error --user-agent Homebrew/2.2.12-7-g105aae4\ \(Macintosh\;\ Intel\ Mac\ OS\ X\ 10.15.3\)\ curl/7.64.1 --retry 3 --location --silent --head --request GET https://github.com/MacDownApp/macdown/releases/download/v0.7.3/MacDown.app.zip
Already downloaded: /Users/czeluff/Library/Caches/Homebrew/downloads/52bbe608e0e7c436a76455a61fb2bea9dac81365b5da23f0acfa680b4819f266--MacDown.app.zip
==> Checking quarantine support
/usr/bin/xattr
/usr/bin/swift /usr/local/Homebrew/Library/Homebrew/cask/utils/quarantine.swift
==> Quarantine is available.
==> Verifying Gatekeeper status of /Users/czeluff/Library/Caches/Homebrew/downloads/52bbe608e0e7c436a76455a61fb2bea9dac81365b5da23f0acfa680b4819f266--MacDown.app.zip
/usr/bin/xattr -p com.apple.quarantine /Users/czeluff/Library/Caches/Homebrew/downloads/52bbe608e0e7c436a76455a61fb2bea9dac81365b5da23f0acfa680b4819f266--MacDown.app.zip
==> /Users/czeluff/Library/Caches/Homebrew/downloads/52bbe608e0e7c436a76455a61fb2bea9dac81365b5da23f0acfa680b4819f266--MacDown.app.zip is quarantined
==> Downloaded to -> /Users/czeluff/Library/Caches/Homebrew/downloads/52bbe608e0e7c436a76455a61fb2bea9dac81365b5da23f0acfa680b4819f266--MacDown.app.zip
==> Verifying SHA-256 checksum for Cask 'macdown'.
zipinfo -1 /Users/czeluff/Library/Caches/Homebrew/downloads/52bbe608e0e7c436a76455a61fb2bea9dac81365b5da23f0acfa680b4819f266--MacDown.app.zip
==> Installing Cask macdown
==> Cask::Installer#stage
==> Extracting primary container
==> Using container class UnpackStrategy::Zip for /Users/czeluff/Library/Caches/Homebrew/downloads/52bbe608e0e7c436a76455a61fb2bea9dac81365b5da23f0acfa680b4819f266--MacDown.app.zip
zipinfo -1 /Users/czeluff/Library/Caches/Homebrew/downloads/52bbe608e0e7c436a76455a61fb2bea9dac81365b5da23f0acfa680b4819f266--MacDown.app.zip
unzip -o /Users/czeluff/Library/Caches/Homebrew/downloads/52bbe608e0e7c436a76455a61fb2bea9dac81365b5da23f0acfa680b4819f266--MacDown.app.zip -d /var/folders/4v/dgtz3tcd2l399m9jxmvcdkwc0000gn/T/d20200408-52407-1ghrcmv
cp -pR /var/folders/4v/dgtz3tcd2l399m9jxmvcdkwc0000gn/T/d20200408-52407-1ghrcmv/MacDown.app/. /usr/local/Caskroom/macdown/0.7.3/MacDown.app
cp: /var/folders/4v/dgtz3tcd2l399m9jxmvcdkwc0000gn/T/d20200408-52407-1ghrcmv/MacDown.app/./Contents/_CodeSignature: Permission denied
==> Purging files for version 0.7.3 of Cask macdown
Error: Failure while executing; `cp -pR /var/folders/4v/dgtz3tcd2l399m9jxmvcdkwc0000gn/T/d20200408-52407-1ghrcmv/MacDown.app/. /usr/local/Caskroom/macdown/0.7.3/MacDown.app` exited with 1. Here's the output:
cp: /var/folders/4v/dgtz3tcd2l399m9jxmvcdkwc0000gn/T/d20200408-52407-1ghrcmv/MacDown.app/./Contents/_CodeSignature: Permission denied

Output of brew cask doctor

==> Homebrew Version
2.2.12-7-g105aae4
==> macOS
10.15.3
==> SIP
Enabled
==> Java
N/A
==> xattr issues
<NONE>
==> Gatekeeper support
Enabled
==> Homebrew Cask Install Location
<NONE>
==> Homebrew Cask Staging Location
/usr/local/Caskroom
==> Homebrew Cask Taps:
/usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask (3520 casks)
==> Contents of $LOAD_PATH
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/ruby-macho-2.2.0/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/rubocop-rspec-1.38.1/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/rubocop-performance-1.5.2/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/rexml-3.2.4/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/plist-3.5.0/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/mechanize-2.7.6/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/activesupport-6.0.2.2/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/zeitwerk-2.3.0/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/tzinfo-1.2.7/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/thread_safe-0.3.6/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/i18n-1.8.2/lib
/usr/local/Homebrew/Library/Homebrew/vendor/bundle/bundler/../ruby/2.6.0/gems/concurrent-ruby-1.1.6/lib/concurrent-ruby
/Library/Ruby/Site/2.6.0
/Library/Ruby/Site/2.6.0/universal-darwin19
/Library/Ruby/Site
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/vendor_ruby/2.6.0
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/vendor_ruby/2.6.0/universal-darwin19
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/vendor_ruby
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/universal-darwin19
/usr/local/Homebrew/Library/Homebrew
==> Environment Variables
LC_ALL="en_US.UTF-8"
PATH="/usr/local/Homebrew/Library/Homebrew/shims/scm:/usr/bin:/bin:/usr/sbin:/sbin"
SHELL="/bin/zsh"

Output of brew tap

homebrew/cask
homebrew/core

[vitorgalvao]

We’re aware. This is an upstream issue.