Explicit require for Set

[marcotc]

As rake moved their require "set"'" statement in 13.0.4#diff-191505f9c8 today, appraisal install started to fail with the error:

$ bundle exec appraisal install
bundler: failed to load command: appraisal (/app/bin/appraisal)
/app/gems/appraisal-2.4.0/lib/appraisal/dependency_list.rb:7:in `initialize': uninitialized constant Appraisal::DependencyList::Set (NameError)
	from /app/gems/appraisal-2.4.0/lib/appraisal/bundler_dsl.rb:13:in `new'
	from /app/gems/appraisal-2.4.0/lib/appraisal/bundler_dsl.rb:13:in `initialize'
	from /app/gems/appraisal-2.4.0/lib/appraisal/appraisal_file.rb:16:in `new'
	from /app/gems/appraisal-2.4.0/lib/appraisal/appraisal_file.rb:16:in `initialize'
	from /app/gems/appraisal-2.4.0/lib/appraisal/appraisal_file.rb:11:in `new'
	from /app/gems/appraisal-2.4.0/lib/appraisal/appraisal_file.rb:11:in `each'
	from /app/gems/appraisal-2.4.0/lib/appraisal/task.rb:32:in `block in initialize'
	from /app/gems/rake-13.0.4/lib/rake/task_manager.rb:232:in `in_namespace'
	from /app/gems/rake-13.0.4/lib/rake/dsl_definition.rb:141:in `namespace'
	from /app/gems/appraisal-2.4.0/lib/appraisal/task.rb:9:in `initialize'
	from /app/gems/appraisal-2.4.0/lib/appraisal.rb:4:in `new'
	from /app/gems/appraisal-2.4.0/lib/appraisal.rb:4:in `<top (required)>'
	from /app/gems/appraisal-2.4.0/bin/appraisal:4:in `require'
	from /app/gems/appraisal-2.4.0/bin/appraisal:4:in `<top (required)>'
	from /app/bin/appraisal:23:in `load'
	from /app/bin/appraisal:23:in `<top (required)>'
	from /app/gems/bundler-2.2.19/lib/bundler/cli/exec.rb:63:in `load'
	from /app/gems/bundler-2.2.19/lib/bundler/cli/exec.rb:63:in `kernel_load'
	from /app/gems/bundler-2.2.19/lib/bundler/cli/exec.rb:28:in `run'
	from /app/gems/bundler-2.2.19/lib/bundler/cli.rb:474:in `exec'
	from /app/gems/bundler-2.2.19/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
	from /app/gems/bundler-2.2.19/lib/bundler/vendor/thor/lib/thor/invocation.rb:127:in `invoke_command'
	from /app/gems/bundler-2.2.19/lib/bundler/vendor/thor/lib/thor.rb:392:in `dispatch'
	from /app/gems/bundler-2.2.19/lib/bundler/cli.rb:30:in `dispatch'
	from /app/gems/bundler-2.2.19/lib/bundler/vendor/thor/lib/thor/base.rb:485:in `start'
	from /app/gems/bundler-2.2.19/lib/bundler/cli.rb:24:in `start'
	from /app/gems/bundler-2.2.19/exe/bundle:49:in `block in <top (required)>'
	from /app/gems/bundler-2.2.19/lib/bundler/friendly_errors.rb:130:in `with_friendly_errors'
	from /app/gems/bundler-2.2.19/exe/bundle:37:in `<top (required)>'
	from /app/bin/bundle:23:in `load'
	from /app/bin/bundle:23:in `<main>'

This fails for any Appraisals file.

This affects Ruby 2.4 up to 3.0, as far as I could test.

This PR adds the require 'set' statement to the file that references the Set class.

[dzunk]

Yes please 🙏 I was wondering why my gem's CI randomly broke...

[dzunk]

Probably should remain consistent with single vs. double quotes

[marcotc]

I tried that at first, but the CI linting bot yield at me for that, so I changed it to double quotes.

Looking at recent changes in the repo, double quotes seems to be the new pattern.

[dzunk]

cc: @nickcharlton would be great to get this into a 2.4.1 patch release

[mhenrixon]

Downgrading rake to 13.0.3 worked for me until we get a new release.

[nickcharlton]

Thanks for fixing this! I'm a bit swamped at the minute, but I'll have time to look properly on Friday and should be able to cut a release.

[ayoa77]

Came here to do just this. Props to you @marcotc!

[nickcharlton]

Funny looking Friday like I thought, but thanks again. I'm going to merge this now and push out a release.