@leo-souza is returning a string, should not be returning a `ActiveSupport::Multibyte::Chars`?
Maybe this broke the build.

Suggestion:
``` ruby
def as_8bit_ascii(string, downcase=false)
  string = string.to_s
  string.downcase! if downcase
  if defined?(Encoding)
    string.dup.force_encoding('BINARY')
  else
    string.mb_chars
  end
end
```