Better general error message for sass parsing.

lib/sass/script/lexer.rb

@@ -56,7 +56,7 @@ module Sass
 
         value = variable || string || number || color || bool || op || ident
         unless value
-          raise SyntaxError.new("Syntax error in '#{@scanner.string}' at '#{@scanner.rest}'.")
+          raise SyntaxError.new("Syntax error in '#{@scanner.string}' at character #{current_position}.")
         end
         Token.new(value.first, value.last, @line, last_match_position)
       end

test/sass/engine_test.rb

@@ -50,7 +50,7 @@ class SassEngineTest < Test::Unit::TestCase
     "@import foo.sass" => "File to import not found or unreadable: foo.sass.",
     "@import templates/basic\n  foo" => "Illegal nesting: Nothing may be nested beneath import directives.",
     "foo\n  @import templates/basic" => "Import directives may only be used at the root of a document.",
-    "!foo = bar baz !" => "Syntax error in 'bar baz !' at '!'.",
+    "!foo = bar baz !" => "Syntax error in 'bar baz !' at character 8.",
     "=foo\n  :color red\n.bar\n  +bang" => "Undefined mixin 'bang'.",
     ".bar\n  =foo\n    :color red\n" => ["Mixins may only be defined at the root of a document.", 2],
     "=foo\n  :color red\n.bar\n  +foo\n    :color red" => "Illegal nesting: Nothing may be nested beneath mixin directives.",