Rakefile need this gem

--- a/Gemfile
+++ b/Gemfile
@@ -463,3 +463,6 @@
 gem 'ipynbdiff', '~> 0.4.7'
 
 gem 'ed25519', '~> 1.3'
+
+# This is required for Rakefile
+gem 'gitlab-dangerfiles'