XcodeGen: Brew install does not currently work

Using the instructions from the README I currently get this:

brew install xcodegen
==> Installing xcodegen from yonaskolb/xcodegen
==> Downloading https://github.com/yonaskolb/XcodeGen/archive/0.6.1.tar.gz
Already downloaded: /Users/dbeard/Library/Caches/Homebrew/xcodegen-0.6.1.tar.gz
==> Building XcodeGen
==> swift build -c release -Xlinker -rpath -Xlinker @executable_path -Xswiftc -static-stdlib
Last 15 lines from /Users/dbeard/Library/Logs/Homebrew/xcodegen/01.swift:
2017-09-13 12:02:33 -0700

swift build -c release -Xlinker -rpath -Xlinker @executable_path -Xswiftc -static-stdlib

error: manifest parse error(s):
sandbox-exec: sandbox_apply_container: Operation not permitted

If reporting this issue please do so to (not Homebrew/brew or Homebrew/core):
yonaskolb/xcodegen

/usr/local/Homebrew/Library/Homebrew/utils/github.rb:226:in `raise_api_error': curl failed!  (GitHub::Error)
curl: (22) The requested URL returned error: 422 Unprocessable Entity
curl: (3) <url> malformed
	from /usr/local/Homebrew/Library/Homebrew/utils/github.rb:184:in `open'
	from /usr/local/Homebrew/Library/Homebrew/utils/github.rb:284:in `search'
	from /usr/local/Homebrew/Library/Homebrew/utils/github.rb:231:in `search_issues'
	from /usr/local/Homebrew/Library/Homebrew/utils/github.rb:244:in `issues_for_formula'
	from /usr/local/Homebrew/Library/Homebrew/exceptions.rb:369:in `fetch_issues'
	from /usr/local/Homebrew/Library/Homebrew/exceptions.rb:365:in `issues'
	from /usr/local/Homebrew/Library/Homebrew/exceptions.rb:419:in `dump'
	from /usr/local/Homebrew/Library/Homebrew/brew.rb:133:in `rescue in <main>'
	from /usr/local/Homebrew/Library/Homebrew/brew.rb:26:in `<main>'