Read a file from a ZipFile and write it to a new ZipFile.

def CopyFileInZip(from_zip, from_name, to_zip, to_name=None):
  """Read a file from a ZipFile and write it to a new ZipFile."""
  data = from_zip.read(from_name)
  if to_name is None:
    to_name = from_name
  to_zip.writestr(to_name, data)