Get undefined method with sprockets 2.0 (can use 2.0.0.beta.15) with Rails 3.1.0.rc5 for Michael Hartl's Rails Tutorial sample_app project

Bundle install is green, but when I run "rake" I get the following:

rake aborted! undefined method `static_root=' for
#<Sprockets::Environment:0x16b6b78> ... Tasks: TOP => default => spec
=> db:tes开发者_如何学JAVAt:prepare => db:abort_if_pending_migrations => environment
(See full trace by running task with --trace)

If I add "gem 'sprockets', '2.0.0.beta.15'" to Gemfile and rebundle and re-rake. Everything is okay.

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I faced same issue,I resolved it by

gem install rails -v=3.1.0.rc8

check it out