Extract the ZipInfo object 'member' to a physical
           file on the path targetpath.

def _extract_member(self, member, targetpath, pwd):
        """Extract the ZipInfo object 'member' to a physical
           file on the path targetpath.
        """
        # build the destination pathname, replacing
        # forward slashes to platform specific separators.
        # Strip trailing path separator, unless it represents the root.
        if (targetpath[-1:] in (os.path.sep, os.path.altsep)
            and len(os.path.splitdrive(targetpath)[1]) > 1):
            targetpath = targetpath[:-1]

        # don't include leading "/" from file name if present
        if member.filename[0] == '/':
            targetpath = os.path.join(targetpath, member.filename[1:])
        else:
            targetpath = os.path.join(targetpath, member.filename)

        targetpath = os.path.normpath(targetpath)

        # Create all upper directories if necessary.
        upperdirs = os.path.dirname(targetpath)
        if upperdirs and not os.path.exists(upperdirs):
            os.makedirs(upperdirs)

        if member.filename[-1] == '/':
            if not os.path.isdir(targetpath):
                os.mkdir(targetpath)
            return targetpath

        source = self.open(member, pwd=pwd)
        target = file(targetpath, "wb")
        shutil.copyfileobj(source, target)
        source.close()
        target.close()

        return targetpath