Allow readers to accept pathlib.Path instances as filenames.

[honnorat]

Allow readers to accept pathlib.Path instances as filenames.

• Closes Allow readers to accept pathlib.Path instances #450
• Tests added
• Tests passed
• Passes git diff origin/master **/*py | flake8 --diff
• Fully documented

[coveralls]

Coverage remained the same at 72.966% when pulling d5d0631 on EXWEXs:fix-pathlib into 2f45b54 on pytroll:master.

[coveralls]

Coverage increased (+0.009%) to 72.975% when pulling 3ad0503 on EXWEXs:fix-pathlib into 2f45b54 on pytroll:master.

[codecov]

Codecov Report

Merging #451 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #451      +/-   ##
==========================================
+ Coverage   72.96%   72.97%   +<.01%     
==========================================
  Files         134      134              
  Lines       17689    17695       +6     
==========================================
+ Hits        12907    12913       +6     
  Misses       4782     4782

Impacted Files	Coverage Δ
satpy/tests/test_readers.py	98.54% <100%> (+0.02%)	⬆️
satpy/tests/reader_tests/test_hdf5_utils.py	92.64% <100%> (+0.1%)	⬆️
satpy/readers/yaml_reader.py	88.02% <100%> (ø)	⬆️

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[djhoese]

Wow is that really all that is needed? Nice.

Would you mind adding a simple unit test? I'm guessing you'll have to add something to check if pathlib is available and skip the test if not (python 2).

[honnorat]

I hope this is enough, I don't know where to test elsewhere.

[djhoese]

I made a small change to how the test is skipped, but otherwise it looks good. One question, since you had to change the fake hdf5 handler to make the test work, does this mean that the base file handler (satpy/readers/file_handlers.py) might also need to be updated? What readers have you tried this with?