gem install rails -v 4.2.4 Failed to install - ruby-on-rails

Question

I receive the following error message when running this command:
gem install rails -v 4.2.4
This is the error:
/Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/yaml.rb:5:in `<top (required)>':
It seems your ruby installation is missing psych (for YAML output).
To eliminate this warning, please install libyaml and reinstall your ruby.
/Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': dlopen(/Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/x86_64-darwin15/psych.bundle, 9): Library not loaded: /usr/local/opt/libyaml/lib/libyaml-0.2.dylib (LoadError)
Referenced from: /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/x86_64-darwin15/psych.bundle
Reason: image not found - /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/x86_64-darwin15/psych.bundle
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/psych.rb:7:in `<top (required)>'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/yaml.rb:6:in `<top (required)>'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems.rb:628:in `load_yaml'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/config_file.rb:326:in `load_file'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/config_file.rb:198:in `initialize'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/gem_runner.rb:75:in `new'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/gem_runner.rb:75:in `do_configuration'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/gem_runner.rb:40:in `run'
from /Users/adamgoldberg/.rvm/rubies/ruby-2.3.0/bin/gem:21:in `<main>'
Please Help - this is causing me nightmares

Answer 1

It seems your ruby installation is missing psych (for YAML output).
Install libyaml with Homebrew: http://brew.sh; then try gem install rails -v 4.2.4
$ brew info libyaml
libyaml: stable 0.1.6 (bottled)
YAML Parser
http://pyyaml.org/wiki/LibYAML
Not installed
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/libyaml.rb
==> Options
--universal
Build a universal binary
$ brew install libyaml
==> Downloading https://homebrew.bintray.com/bottles/libyaml-0.1.6_1.el_capitan.bottle.tar.gz
######################################################################## 100.0%
==> Pouring libyaml-0.1.6_1.el_capitan.bottle.tar.gz
🍺 /usr/local/Cellar/libyaml/0.1.6_1: 8 files, 312.8K
REINSTALL RUBY
If the above solution doesn't work for you, reinstall Ruby from scratch with rvm or rbenv,
1) Try the instructions on this accepted answer: https://stackoverflow.com/a/38194139/1076207
—OR—
2) Remove all rvm files, then reinstall rvm: https://stackoverflow.com/a/38158619/1076207
—OR—
3) Remove all rvm files, then install rbenv: https://stackoverflow.com/a/38194231/1076207
After using one of the three options above, use http://bundler.io to install Rails:
$ mkdir ~/Documents/Repo
$ cd ~/Documents/Repo
$ gem install bundler
[…]
$ bundle init
Writing new Gemfile to /Users/username/Documents/Repo/Gemfile
$ echo "gem 'rails', '4.2.4'" >> Gemfile
$ bundle install
[…]
$ bundle exec rails new project_name
[…]
$ cd project_name
Personally, I recommend 3) switch to rbenv—I did.

Answer 2

The error itself clearly says that you should install libyaml first and then re-install your ruby. You can do it by running following commands.
sudo apt-get install libtool
rvm package install libyaml
rvm reinstall ruby-2.3.0
for more reference please see this answer