How do I find out which gem has a specific dependency?

I commented out a gem, but 'bundle install' still won't run. How do I find out which gem has a dependency on sys-proctable?

$ bundle install
Fetching gem metadata from https://rubygems.org/.........
Fetching gem metadata from https://rubygems.org/..
Resolving dependencies...
Could not find sys-proctable-0.9.2 in any of the sources

$ grep proctable Gemfile
  #gem 'sys-proctable', '0.9.2', :path => "vendor/gems"

$ bundle list
Resolving dependencies...
Could not find gem 'rspec-rails (= 2.11.0) ruby' in the gems available on this machine.

$ bundle viz
Resolving dependencies...
Could not find gem 'rspec-rails (= 2.11.0) ruby' in the gems available on this machine.

$ bundle -v
Bundler version 1.3.0

$ ruby -v
ruby 1.9.3p385 (2013-02-06 revision 39114) [i386-cygwin]

Gemfile: http://pastebin.com/9WWMfKtv

I've already tried these troubleshooting steps: https://github.com/carlhuda/bundler/blob/1-2-stable/ISSUES.md

In the bash shell you can do:

gem dependency name_of_the_gem --reverse-dependencies

For instance:

$ gem dependency activesupport --reverse-dependencies                        
Gem activesupport-2.3.14
Used by
actionpack-2.3.14 (activesupport (= 2.3.14))
activerecord-2.3.14 (activesupport (= 2.3.14))
activeresource-2.3.14 (activesupport (= 2.3.14))

I know this answer includes a link, but this is not a link specific answer

You can always check the reverse dependencies of a gem on rubygems.org. There's a link on the right side panel on the website.

Or you can visit the site

> https://rubygems.org/gems/{gem_name}/reverse_dependencies

So, in your case

https://rubygems.org/gems/sys-proctable/reverse_dependencies

> How do I find out which gem has a dependency on sys-proctable?

Try the bundler-why plugin (inspired by yarn why)

bundler plugin install bundler-why
bundle why tzinfo
# ransack -> activesupport -> tzinfo
# rspec-rails -> activesupport -> tzinfo
# business_time -> tzinfo

gem dependency --reverse-dependencies will traverse a single edge of the paths. In comparison, bundle why will traverse all edges.