old_contents: """
  escape/unescape routines available for backends which need
  alphanumeric usernames, services, or other values
  """
  
  import re
  import string
  import sys
  
  # True if we are running on Python 3.
  # taken from six.py
  PY3 = sys.version_info[0] == 3
  
  # allow use of unicode literals
  if PY3:
      def u(s):
          return s
  
      def _unichr(c):
          return chr(c)
  else:
      def u(s):
          return s.decode('utf-8')
  
      def _unichr(c):
          return unichr(c)  # noqa: F821
  
  LEGAL_CHARS = (
      getattr(string, 'letters', None)  # Python 2
      or getattr(string, 'ascii_letters')  # Python 3
  ) + string.digits
  
  ESCAPE_FMT = "_%02X"
  
  
  def _escape_char(c):
      "Single char escape. Return the char, escaped if not already legal"
      if isinstance(c, int):
          c = _unichr(c)
      return c if c in LEGAL_CHARS else ESCAPE_FMT % ord(c)
  
  
  def escape(value):
      """
      Escapes given string so the result consists of alphanumeric chars and
      underscore only.
      """
      return "".join(_escape_char(c) for c in value.encode('utf-8'))
  
  
  def _unescape_code(regex_match):
      ordinal = int(regex_match.group('code'), 16)
      if sys.version_info >= (3,):
          return bytes([ordinal])
      return chr(ordinal)
  
  
  def unescape(value):
      """
      Inverse of escape.
      """
      re_esc = re.compile(
          # the pattern must be bytes to operate on bytes
          ESCAPE_FMT.replace('%02X', '(?P<code>[0-9A-Fa-f]{2})').encode('ascii')
      )
      return re_esc.sub(_unescape_code, value.encode('ascii')).decode('utf-8')
  
new_contents: """
  escape/unescape routines available for backends which need
  alphanumeric usernames, services, or other values
  """
  
  import re
  import string
  import sys
  
  # True if we are running on Python 3.
  # taken from six.py
  PY3 = sys.version_info[0] == 3
  
  # allow use of unicode literals
  if PY3:
      def u(s):
          return s
  else:
      def u(s):
          return s.decode('utf-8')
  
  _unichr = chr if PY3 else unichr  # noqa: F821
  
  LEGAL_CHARS = (
      getattr(string, 'letters', None)  # Python 2
      or getattr(string, 'ascii_letters')  # Python 3
  ) + string.digits
  
  ESCAPE_FMT = "_%02X"
  
  
  def _escape_char(c):
      "Single char escape. Return the char, escaped if not already legal"
      if isinstance(c, int):
          c = _unichr(c)
      return c if c in LEGAL_CHARS else ESCAPE_FMT % ord(c)
  
  
  def escape(value):
      """
      Escapes given string so the result consists of alphanumeric chars and
      underscore only.
      """
      return "".join(_escape_char(c) for c in value.encode('utf-8'))
  
  
  def _unescape_code(regex_match):
      ordinal = int(regex_match.group('code'), 16)
      if sys.version_info >= (3,):
          return bytes([ordinal])
      return chr(ordinal)
  
  
  def unescape(value):
      """
      Inverse of escape.
      """
      re_esc = re.compile(
          # the pattern must be bytes to operate on bytes
          ESCAPE_FMT.replace('%02X', '(?P<code>[0-9A-Fa-f]{2})').encode('ascii')
      )
      return re_esc.sub(_unescape_code, value.encode('ascii')).decode('utf-8')
  
subject: Use single, direct assignment for _unichr.