class Sass::Script::Value::String

def self.quote(contents, opts = {})

Whether to quote strings for Sass source, as opposed to CSS. Defaults to `false`.
@options opts :sass [String]
always emitted unquoted. If `nil`, quoting is determined automatically.
The preferred quote style for quoted strings. If `:none`, strings are
@options opts :quote [String]

Returns the quoted string representation of `contents`. 
def self.quote(contents, opts = {})
  quote = opts[:quote]
  # Short-circuit if there are no characters that need quoting.
  unless contents =~ /[\n\\"']|\#\{/
    quote ||= '"'
    return "#{quote}#{contents}#{quote}"
  end
  if quote.nil?
    if contents.include?('"')
      if contents.include?("'")
        quote = '"'
      else
        quote = "'"
      end
    else
      quote = '"'
    end
  end
  # Replace single backslashes with multiples.
  contents = contents.gsub("\\", "\\\\\\\\")
  # Escape interpolation.
  contents = contents.gsub('#{', "\\\#{") if opts[:sass]
  if quote == '"'
    contents = contents.gsub('"', "\\\"")
  else
    contents = contents.gsub("'", "\\'")
  end
  contents = contents.gsub(/\n(?![a-fA-F0-9\s])/, "\\a").gsub("\n", "\\a ")
  "#{quote}#{contents}#{quote}"
end