text: def check(got, expected, expected_builtin=None):
    if got is None:  # Absence of comment is equivalent to empty comment.
        got = ''
  
    if got != expected:
      import re
      p = re.compile(r'^[+-]([^+-].*\S)?(\s+)$', re.M)
  
      def make_trailing_spaces_visible(str):
          def replace_trailing_spaces(match):
              res = match.group(0)
              spaces = match.group(2)
              if spaces is not None:
                  res = res + "{+%d trailing spaces}" % len(spaces)
              return res
          return re.sub(p, replace_trailing_spaces, str)
  
      from difflib import unified_diff
      diff = unified_diff(expected.splitlines(True),
                          got.splitlines(True), "expected", "got")
      lines = []
      for line in diff:
          line = make_trailing_spaces_visible(line.strip("\r\n"))
          lines.append(line + "\n")
  
      raise RuntimeError("Comments don't match:\n" + "".join(lines))
  