old_contents: 
  import subprocess
  
  def is_binary_file(fname):
      """Attempt to guess if 'fname' is a binary file heuristically.
  
      The algorithm has many flaws. Use with caution.
      It assumes that if a part of the file has NUL bytes
      or has more control characters than text characters,
      it is probably a binary file.
      An ASCII compatible character set is assumed.
  
      Returns True if 'fname' appears to be a binary file.
      """
      with open(fname, 'rb') as fh:
          chunk = fh.read(1024)
  
          if not chunk: # Empty file
              return False
  
          if b'\x00' in chunk: # Has NUL bytes
              return True
  
          ncontrol = control_char_count(chunk)
          ntext = len(chunk) - ncontrol
          return ncontrol > ntext
  
  def is_control_char(c):
      """Return True if 'c' is a control character.
  
      c is considered a control character if
      it is outside of the extended ASCII set or
      is a control character below 33.
      An ASCII compatible character set is assumed.
      """
      charcode = ord(c)
      return (charcode < 33 or
              charcode > 255)
  
  def control_char_count(data):
      """Return the count of control characters in 'data'."""
      n = 0
      for c in data:
          if is_control_char(c):
              n += 1
      return n
  
new_contents: 
  def is_binary_file(fname):
      """Attempt to guess if 'fname' is a binary file heuristically.
  
      The algorithm has many flaws. Use with caution.
      It assumes that if a part of the file has NUL bytes
      or has more control characters than text characters,
      it is probably a binary file.
      An ASCII compatible character set is assumed.
  
      Returns True if 'fname' appears to be a binary file.
      """
      with open(fname, 'rb') as fh:
          chunk = fh.read(1024)
  
          if not chunk: # Empty file
              return False
  
          if b'\x00' in chunk: # Has NUL bytes
              return True
  
          ncontrol = control_char_count(chunk)
          ntext = len(chunk) - ncontrol
          return ncontrol > ntext
  
  def is_control_char(c):
      """Return True if 'c' is a control character.
  
      c is considered a control character if
      it is outside of the extended ASCII set or
      is a control character below 33.
      An ASCII compatible character set is assumed.
      """
      charcode = ord(c)
      return (charcode < 33 or
              charcode > 255)
  
  def control_char_count(data):
      """Return the count of control characters in 'data'."""
      n = 0
      for c in data:
          if is_control_char(c):
              n += 1
      return n
  
subject: Remove unused module import