NoMethodError: undefined method `spec' for nil:NilClass - active_utils, factory_girl and more gems failing

Question

Out of nowhere, and without changing anything, I've started getting this error (and so did other people on the team).

This is happening for some gems (the ones specifying a git branch) and is only happening when we recreate the environment (in vagrant). We didn't change anything.

Any ideas? More info follows:

Using active_utils (2.0.0) from git://github.com/Shopify/active_utils.git (at v2.0.0)
NoMethodError: undefined method `spec' for nil:NilClass
An error occurred while installing active_utils (2.0.0), and Bundler cannot continue.
Make sure that `gem install active_utils -v '2.0.0'` succeeds before bundling.

Using factory_girl (2.6.5) from https://github.com/thoughtbot/factory_girl (at 2.6.x)
NoMethodError: undefined method `spec' for nil:NilClass
An error occurred while installing factory_girl (2.6.5), and Bundler cannot continue.
Make sure that `gem install factory_girl -v '2.6.5'` succeeds before bundling.

• Running "gem install active_utils -v '2.0.0'" works but bundle always fails.
• Cleared gem cache, but didn't help

Seems like it's all entries in Gemfile specifying a branch that started failing.

gem 'active_utils', :git => 'git://github.com/Shopify/active_utils.git', :branch => 'v2.0.0'
gem "will_paginate", :git => "git://github.com/mislav/will_paginate.git", :branch => "2-3-stable"

Answer 1

So, turns out this was caused because of a recent upgrade to RubyGems. Forcing a previous version worked.

gem update --system 2.4.8