Add gem filter for default gem path since it maybe different than the set of gem paths

railties/lib/rails/backtrace_cleaner.rb

@@ -32,7 +32,7 @@ def initialize
     
     private
       def add_gem_filters
-        Gem.path.each do |path|
+        (Gem.path + [Gem.default_dir]).uniq.each do |path|
           # http://gist.github.com/30430
           add_filter { |line| line.sub(/(#{path})\/gems\/([a-z]+)-([0-9.]+)\/(.*)/, '\2 (\3) \4')}
         end

railties/test/backtrace_cleaner_test.rb

@@ -14,13 +14,13 @@ def setup
       @test = TestWithBacktrace.new
       @backtrace = [ './test/rails/benchmark_test.rb', './test/rails/dependencies.rb', '/opt/local/lib/ruby/kernel.rb' ]
     end
-    
+
     test "test with backtrace should use the rails backtrace cleaner to clean" do
       Rails.stubs(:backtrace_cleaner).returns(stub(:clean))
       Rails.backtrace_cleaner.expects(:clean).with(@backtrace, nil)
       @test.filter_backtrace(@backtrace)
     end
-    
+
     test "filter backtrace should have the same arity as Test::Unit::Util::BacktraceFilter" do
       assert_nothing_raised do
         @test.filter_backtrace(@backtrace, '/opt/local/lib')