Show real LoadError on helpers require

When helper try to require missing file rails will throw exception about
missing helper.

  # app/helpers/my_helper.rb

  require 'missing'

  module MyHelper
  end

And when we try do load helper

  class ApplicationController
    helper :my
  end

Rails will throw exception. This is wrong because there is a helper
file.

  Missing helper file helpers/my_helper.rb

Now when helper try to require non-existed file rails will throw proper
exception.

  No such file to load -- missing

1 files changed, 6 insertions, 1 deletions

diff --git a/actionpack/lib/abstract_controller/helpers.rb b/actionpack/lib/abstract_controller/helpers.rb
index 5ae8c6c3b0..a928205963 100644
--- a/actionpack/lib/abstract_controller/helpers.rb
+++ b/actionpack/lib/abstract_controller/helpers.rb
@@ -150,7 +150,12 @@ module AbstractController
           @error = error
           @path  = "helpers/#{path}.rb"
           set_backtrace error.backtrace
-          super("Missing helper file helpers/%s.rb" % path)
+
+          if error.path =~ /^#{path}(\.rb)?$/
+            super("Missing helper file helpers/%s.rb" % path)
+          else
+            raise error
+          end
         end
       end