Let the people know what file path failed the compile

lib/requirejs/rails/builder.rb

@@ -6,17 +6,19 @@
 module Requirejs::Rails
   class Builder
     # config should be an instance of Requirejs::Rails::Config
-    
+
     def initialize(config)
       @config = config
     end
-    
-    def build      
+
+    def build
       @config.tmp_dir
     end
 
     def digest_for(path)
       Rails.application.assets.file_digest(path).hexdigest
+    rescue StandardError => e
+      raise ArgumentError, "digest_for(#{path}) failed with #{e.class}: #{e.message}\n#{e.backtrace[0..4].join("\n")}"
     end
 
     def generate_rjs_driver
@@ -26,4 +28,4 @@ def generate_rjs_driver
       end
     end
   end
-end
+end