找不到 gem 'sqlite3 (>= 0) ruby​​'

我正在学习 Ruby on Rails，并且我从 Ryan Bigg 的博客和 Agile Wed Development 一书中关注了 RVM 和 Rails 的安装.这以前在我家里的电脑上工作过，但在工作中它给了我错误:

I am learning Ruby on Rails and I followed the installation of RVM and Rails from Ryan Bigg's blog and the Agile Wed Development book. This has worked previously on my PC at home, but at work it gives me the error:

depot$ rails -v
Could not find gem 'sqlite3 (>= 0) ruby' in the gems available on this machine.
Run `bundle install` to install missing gems.

我正在尝试生成一个脚手架，但这就是我得到的:

I am trying to generate a scaffold but this is what i get:

depot$ rails generate scaffold Product \ title:string description:text image_url:text price:decimal
Could not find gem 'sqlite3 (>= 0) ruby' in the gems available on this machine.
Run `bundle install` to install missing gems.

我安装了 sqlite3，RVM 1.9.2-p320，并在 Ubuntu 11.04 上运行.

I have sqlite3 installed, RVM 1.9.2-p320, and running on Ubuntu 11.04.

任何想法可能导致此问题以及如何解决它?

Any ideas what can be causing this and how to fix it?