Added more informative error message for "file not found" situation i…

…n send_file rails#484 [Alexey]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@427 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_controller/base.rb

@@ -441,7 +441,7 @@ def render_nothing(status = nil)
       # http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9
       # for the Cache-Control header spec.
       def send_file(path, options = {}) #:doc:
-        raise MissingFile, path unless File.file?(path) and File.readable?(path)
+        raise MissingFile, "Cannot read file #{path}" unless File.file?(path) and File.readable?(path)
 
         options[:length]   ||= File.size(path)
         options[:filename] ||= File.basename(path)