0
 ?÷     _INET6, socket.SOCK_STREAM)
            sock.bind((HOSTv6, 0))
            return True
        except OSError:
            pass
        finally:
            if sock:
                sock.close()
    return False

IPV6_ENABLED = _is_ipv6_enabled()

FUZZ = 1e-6

def fcmp(x, y): # fuzzy comparison function
    if isinstance(x, float) or isinstance(y, float):
        try:
            fuzz = (abs(x) + abs(y)) * FUZZ
            if abs(x-y) <= fuzz:
                return 0
        except:
            pass
    elif type(x) == type(y) and isinstance(x, (tuple, list)):
        for i in range(min(len(x), len(y))):
            outcome = fcmp(x[i], y[i])
            if outcome != 0:
                return outcome
        return (len(x) > len(y)) - (len(x) < len(y))
    return (x > y) - (x < y)


# A constant likely larger than the underlying OS pipe buffer size, to
# make writes blocking.
# Windows limit seems to be around 512 B, and many Unix kernels have a
# 64 KiB pipe buffer size or 16 * PAGE_SIZE: take a few megs to be sure.
# (see issue #17835 for a discussion of this number).
PIPE_MAX_SIZE = 4 *1024 * 1024 + 1


try:
    unicode
    have_unicode = True
except NameError:
    have_unicode = False

is_jython = sys.platform.startswith('java')

# Filename used for testing
if os.name == 'java':
    # Jython disallows @ in module names
    TESTFN = '$test'
elif os.name == 'riscos':
    TESTFN = 'testfile'
else:
    TESTFN = '@test'
    # Unicode name only used if TEST_FN_ENCODING exists for the platform.
    if have_unicode:
        # Assuming sys.getfilesystemencoding()!=sys.getdefaultencoding()
        # TESTFN_UNICODE is a filename that can be encoded using the
        # file system encoding, but *not* with the default (ascii) encoding
        if isinstance('', unicode):
            # python -U
            # XXX perhaps unicode() should accept Unicode strings?
            TESTFN_UNICODE = "@test-\xe0\xf2"
        else:
            # 2 latin characters.
            TESTFN_UNICODE = unicode("@test-\xe0\xf2", "latin-1")
        TESTFN_ENCODING = sys.getfilesystemencoding()
        # TESTFN_UNENCODABLE is a filename that should *not* be
        # able to be encoded by *either* the default or filesystem encoding.
        # This test really only makes sense on Windows NT platforms
        # which have special Unicode support in posixmodule.
        if (not hasattr(sys, "getwindowsversion") or
                sys.getwindowsversion()[3] < 2): #  0=win32s or 1=9x/ME
            TESTFN_UNENCODABLE = None
        else:
            # Japanese characters (I think - from bug 846133)
            TESTFN_UNENCODABLE = eval('u"@test-\u5171\u6709\u3055\u308c\u308b"')
            try:
                # XXX - Note - should be using TESTFN_ENCODING here - but for
                # Windows, "mbcs" currently always operates as if in
                # errors=ignore' mode - hence we get '?' characters rather than
                # the exception.  'Latin1' operates as we expect - ie, fails.
                # See [ 850997 ] mbcs encoding ignores errors
                TESTFN_UNENCODABLE.encode("Latin1")
            except UnicodeEncodeError:
                pass
            else:
                print \
                'WARNING: The filename %r CAN be encoded by the filesystem.  ' \
                'Unicode filename tests may not be effective' \
                % TESTFN_UNENCODABLE


# Disambiguate TESTFN for parallel testing, while letting it remain a valid
# module name.
TESTFN = "{}_{}_tmp".format(TESTFN, os.getpid())

# Save the initial cwd
SAVEDCWD = os.getcwd()

@contextlib.contextmanager
def change_cwd(path, quiet=False):
    """Return a context manager that changes the current working directory.

    Arguments:

      path: the directory to use as the temporary current working directory.

      quiet: if False (the default), the context manager raises an exception
        on error.  Otherwise, it issues only a warning and keeps the current
        working directory the same.

    """
    saved_dir = os.getcwd()
    try:
        os.chdir(