os.path.sep is not changed after switching fs.os to linux

[hard7]

Describe the bug
I'm running tests under windows using fs.os = OSType.LINUX. I noticed that os.path.sep is not faked.

How To Reproduce

import os
import pyfakefs
from pyfakefs.fake_filesystem import OSType


def test_sep_linux(fs):
    fs.os = OSType.LINUX
    assert os.path.sep == "/"
    # FAILED
    # Expected :/
    # Actual   :\\

Enviroment

>python -c "import platform; print(platform.platform())"
Windows-10-10.0.18362-SP0

>python -c "import sys; print('Python', sys.version)"
Python 3.6.8 (tags/v3.6.8:3c6b436a57, Dec 24 2018, 00:16:47) [MSC v.1916 64 bit (AMD64)]

>python -c "from pyfakefs.fake_filesystem import __version__; print('pyfakefs', __version__)"
pyfakefs 4.3.2

[mrbean-bremen]

Thanks - good catch! The same is true for os.sep, os.altsep, and os.path.altsep. Changing the OS type does not reset them.