Fix _dict_from_slots, solves Path comparison

[artemisart]

Hello, I figured out some __slots__ could be not set which makes getattr fails and so DeepDiff._dict_from_slots fails, which is what makes Path comparison impossible currently:

from pathlib import Path

obj = Path('/test/yo')
keys = [key for cls in obj.__class__.__mro__ for key in getattr(cls, '__slots__', ())]
print(keys)
{k: getattr(obj, k, 'not present') for k in keys}
# gives:
['_drv', '_root', '_parts', '_str', '_hash', '_pparts', '_cached_cparts']
{'_drv': '',
 '_root': '/',
 '_parts': ['/', 'test', 'yo'],
 '_str': 'not present',
 '_hash': 'not present',
 '_pparts': 'not present',
 '_cached_cparts': 'not present'}

I fixed this with a hasattr in _dict_from_slots.

Impact:

from deepdiff import DeepDiff
from pathlib import Path

DeepDiff(Path('a'), Path('b/b'))
# Before this change
# {'unprocessed': ['root: a and b/b']}
# After this change
# {'values_changed': {'root._parts[0]': {'new_value': 'b', 'old_value': 'a'}}, 'iterable_item_added': {'root._parts[1]': 'b'}}

Solves #231

[seperman]

@artemisart Thanks for making a PR!
Interesting, so far I have only used os.path. I learned something today.
Can you please fix the failing test test_bad_attribute and add your name and info to the bottom of AUTHORS.md please?

[artemisart]

@seperman fixed!
I'm not sure what was expected for this test, hasattr(Bad(), 'x') returns False so now it doesn't fail anymore, is this ok?

[seperman]

LGTM

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.55%. Comparing base (6d8a4c7) to head (ce1c8fb).
Report is 6 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #480      +/-   ##
==========================================
- Coverage   96.70%   96.55%   -0.16%     
==========================================
  Files          14       14              
  Lines        3946     3946              
==========================================
- Hits         3816     3810       -6     
- Misses        130      136       +6     

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[seperman]

@artemisart We iterate through slot values to compare objects. Before your fix, we would have not processed the Bad() object. Now we process them. Not a super useful test after your fix, I agree.

[artemisart]

Note: you can close #231