Updating to Rails 3 on Mac OS X

Hello, I'm working to install Rails 3 (pre) on my Mac, from the Rails
blog post it says to run:

gem install rails --pre

After running that command I get the following errors:

WARNING: Installing to ~/.gem since /Library/Ruby/Gems/1.8 and
    /usr/bin aren't both writable.
WARNING: You don't have /Users/myusername/.gem/ruby/1.8/bin in your
PATH,
    gem executables will not run.
ERROR: Error installing rails:
  activemodel requires builder (~> 2.1.2, runtime)

was there a step required before running the install that wasn't
mentioned on the blog post?
http://weblog.rubyonrails.org/2010/8/24/rails-3-0-release-candidate-2

Thanks

Running "sudo gem install rails --pre" seemed to make it happier, only
error'd now with:

ERROR: Error installing rails:
  activemodel requires builder (~> 2.1.2, runtime)

Update 3, after getting all the dependencies installed, it's still
erroring:

sudo gem install rails --pre
Successfully installed rails-3.0.0.rc2
1 gem installed
Installing ri documentation for rails-3.0.0.rc2...
File not found: lib

Ideas?

nobosh wrote:

Update 3, after getting all the dependencies installed, it's still
erroring:

sudo gem install rails --pre
Successfully installed rails-3.0.0.rc2
1 gem installed
Installing ri documentation for rails-3.0.0.rc2...
File not found: lib

Ideas?

It looks like it actually installed, it just had trouble building
ri/rdocs. You can disable building the local documentation with --no-ri
and --no-rdoc, but there really shouldn't be a problem with that step of
a gem install.

If you wait a few hours you can skip the whole "--pre" business
altogether, as 3.0.0 will be released =)

lol can't wait. Your trick below worked. Thanks. I'm looking forward
to upgrading in a few hours!