Support pathlib2

[sk-]

First of all thanks for this project, it's really useful. However, it'd be great if there was support for pathlib2.

In my code I'm importing it as import pathlib2 as pathlib. Which gets patched by pyfakefs, however the patch uses the system pathlib, which means that in my case it only works for Python 3.5 and 3.6, as I'm using the exist_ok argument of mkdir. In Python 3.4 I get the following error:

TypeError: mkdir() got an unexpected keyword argument 'exist_ok' 

And in Python 2.7 the module is not patched at all.

I already managed to get this to work in Python 2.7 (and probably in 3.4),

In my test I had to add

def setUp():
  from pyfakefs import fake_pathlib
  self.modules_to_patch = {'pathlib': fake_pathlib.FakePathlibModule}
  self.setUpPyfakefs()

and I had to change fake_pathlib.py as following

try:
  import pathlib2 as pathlib
except ImportError:
  import pathlib
try:
  from urllib.parse import quote_from_bytes as urlquote_from_bytes
except ImportError:
  from urllib import quote as urlquote_from_bytes

Let me know if you would be interested in accepting this change, so I could prepare a patch.

[mrbean-bremen]

Sure, that sounds helpful. I actually wasn't aware of pathlib2, but we did something similar with the scandir module which is a backport of scandir to Python < 3.5.
And nice to know that modules_to_patch has been used by someone :)

[matthew16550]

There is another difficulty using pathlib2 with Python 2.7, the version checking in FakePath.resolve() prevents using strict=False.

e.g.

def test_resolve(fs):
    Path('foo').resolve(False)

Causes:
TypeError: resolve() got an unexpected keyword argument 'strict'

[mrbean-bremen]

Yes, the version checking has been made for pathlib only - the checks have to be changed for pathlib2 support.
@sk- - are you still working on the PR? Do you need help?

[sk-]

@mrbean-bremen sorry I don't have the time to prepare the PR. Feel free to use any of the code snippets if they are of any help.

[matthew16550]

@mrbean-bremen I probably have time this weekend if you would like me to make a PR?

[mrbean-bremen]

@sk- no problem, thanks!
@matthew16550 - thanks for the offer - sure, we always welcome contributions! If you've got the time, please go ahead!

[mrbean-bremen]

Implemented in #422.
Thanks for your contribution and your patience!