gdk doctor errors outside of GDK.root

Overview

When running gdk doctor outside the GDK.root, the following occurs:

$ gdk doctor
(in /Users/ash/src/gdk/gdk-primary)
Traceback (most recent call last):
	16: from /Users/ash/.rbenv/versions/2.6.5/bin/gdk:23:in `<main>'
	15: from /Users/ash/.rbenv/versions/2.6.5/bin/gdk:23:in `load'
	14: from /Users/ash/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/gitlab-development-kit-0.2.5/bin/gdk:125:in `<top (required)>'
	13: from /Users/ash/.rbenv/versions/2.6.5/lib/ruby/gems/2.6.0/gems/gitlab-development-kit-0.2.5/bin/gdk:74:in `launcher_main'
	12: from /Users/ash/src/gdk/gdk-primary/lib/gdk.rb:115:in `main'
	11: from /Users/ash/src/gdk/gdk-primary/lib/gdk/command/doctor.rb:15:in `run'
	10: from /Users/ash/src/gdk/gdk-primary/lib/gdk/command/doctor.rb:27:in `diagnostic_results'
	 9: from /Users/ash/src/gdk/gdk-primary/lib/gdk/command/doctor.rb:27:in `each_with_object'
	 8: from /Users/ash/src/gdk/gdk-primary/lib/gdk/command/doctor.rb:27:in `each'
	 7: from /Users/ash/src/gdk/gdk-primary/lib/gdk/command/doctor.rb:28:in `block in diagnostic_results'
	 6: from /Users/ash/src/gdk/gdk-primary/lib/gdk/diagnostic/pending_migrations.rb:10:in `diagnose'
	 5: from /Users/ash/src/gdk/gdk-primary/lib/shellout.rb:12:in `run'
	 4: from /Users/ash/src/gdk/gdk-primary/lib/shellout.rb:40:in `capture'
	 3: from /Users/ash/.rbenv/versions/2.6.5/lib/ruby/2.6.0/open3.rb:281:in `capture3'
	 2: from /Users/ash/.rbenv/versions/2.6.5/lib/ruby/2.6.0/open3.rb:101:in `popen3'
	 1: from /Users/ash/.rbenv/versions/2.6.5/lib/ruby/2.6.0/open3.rb:213:in `popen_run'
/Users/ash/.rbenv/versions/2.6.5/lib/ruby/2.6.0/open3.rb:213:in `spawn': No such file or directory - gitlab (Errno::ENOENT)