Q:

Rails gem update not working (version 4.1.1 to 4.2.0) as a solution to "warning: circular argument reference" error

I keep getting the following error when I run any sort of rake command, and in particular rake db:seed which will abort without completing:
$ rake db:seed
/Users/rachel/.rvm/gems/ruby-2.2.0@rails4.2/gems/activesupport-4.1.1/lib/active_support/values/time_zone.rb:285: warning: circular argument reference - now
rake aborted!
ActiveRecord::UnknownAttributeError: unknown attribute: description

I did some research and discovered this is an error (I think?) caused by an incompatible gem in Rails 4.1.9 so I was hoping to create a new rvm to update Rails to 4.2.0 so I can proceed with my projects. However, every time I try to update Rails it says 'installed' but fails to actually install into the ruby version I created. Here's the typical command line pattern when I try to update Rails:
$ rvm gemset create rails420
ruby-2.2.0 - #gemset created /Users/rachel/.rvm/gems/ruby-2.2.0@rails420
ruby-2.2.0 - #generating rails420 wrappers........
$ rvm 2.2.0@rails420
$ gem install rails -v 4.2.0
Fetching: rails-4.2.0.gem (100%)
Successfully installed rails-4.2.0
Parsing documentation for rails-4.2.0
Installing ri documentation for rails-4.2.0
Done installing documentation for rails after 339 seconds
1 gem installed
$ rvm 2.2.0@rails420
$ rails --version
Rails 4.1.1

Basically, it installs Rails 4.2.0 but then says it's not installed when I check the version immediately after installation. Any ideas for how I can either solve the error or get the Rails gem to update correctly in my rvm? 

A:

Try the following : 
rvm use ruby-2.2.0@rails4.2 --create
gem install rails
rails -v

This should give you rails 4.2

