Parse fileobj for a shebang.

def _parse(fileobj):
    """Parse fileobj for a shebang."""
    fileobj.seek(0)
    try:
        part = fileobj.read(2)
    except UnicodeDecodeError:
        part = ""

    if part == "#!":
        shebang = shlex.split(fileobj.readline().strip())
        if (platform.system() == "Windows" and
                len(shebang) and
                os.path.basename(shebang[0]) == "env"):
            return shebang[1:]

        return shebang

    return []