Calibration mode can now be passed via a keyword argument

[ColinDuff]

This PR includes the code need to pass the Calibration mode , needed for MSG Calibration, using keyword arguments

This would close #521 if approved

flake8 passed for all 3 files

[djhoese]

Looks good. I have few code cleanup things and other suggestions that I'd like to discuss. See comments below.

[coveralls]

Coverage increased (+0.1%) to 78.223% when pulling 6747065 on ColinDuff:gsics_fix into f3358ca on pytroll:master.

[codecov]

Codecov Report

Merging #543 into master will decrease coverage by <.01%.
The diff coverage is 76.92%.

@@            Coverage Diff             @@
##           master     #543      +/-   ##
==========================================
- Coverage   78.07%   78.07%   -0.01%     
==========================================
  Files         137      137              
  Lines       19890    19894       +4     
==========================================
+ Hits        15530    15533       +3     
- Misses       4360     4361       +1

Impacted Files	Coverage Δ
satpy/readers/__init__.py	95.12% <100%> (ø)	⬆️
satpy/readers/yaml_reader.py	92.6% <100%> (+0.03%)	⬆️
satpy/readers/seviri_l1b_native.py	51.32% <50%> (-0.02%)	⬇️

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[mraspaud]

Good job! A couple of things missing:

• Documentation about the calibration mode switch (could be done in the docstring of the native_msg module)
• Tests

Also, would this work with hrit data too ?

[ColinDuff]

using of the calibration mode kwarg was added to the native_msg_reader class.
A test for the gsics calibration mode can be added later if that is ok
I dont use hrit_msg format so i cant easily test any changes - we will do this later in a separate pr

[mraspaud]

Looks good. Just a simple test and we're good to merge imo.

[ColinDuff]

Re creating a test: In theory should we not instantiate a Scene object for native_msg reader and check the calibration mode but the init method tries to open/read in an actual file to read the header and trailer. I am not sure how to create a test for this scenario.

[mraspaud]

You could do one test for instantiating the file handler with calib_mode=gsics and make sure the right part of the metadata is accessed, and another one that instantiates a scene object with a fake filehandler, to make sure the fh_kwargs are passed to the filehandler's __init__.

[ColinDuff]

Re creating a test. I will wait until the test reader name changes are in master if thats ok

[djhoese]

This PR needs a merge with master to fix the conflicts.

[sfinkens]

@ColinDuff I would like to propose adding a line VIS_CHANNELS = ['HRV', 'VIS006', 'VIS008', 'IR_016'] to satpy.readers.seviri_base.py which can then be used by both the native and the HRIT reader (see https://github.com/pytroll/satpy/pull/636/files#diff-6638815b577a979fa2e187c166216a28).

[mraspaud]

@ColinDuff Where are we with this PR ? It would be nice to see the conflicts fixed and the tests implemented so that we can merge it.

[ColinDuff]

apologies but i have to concentrate on a new MPEF release for now. When i have time i can resolve the issues and have the PR in a state to be merged. will try to do so soon

[ColinDuff]

just pushed to get into sync with satpy master, new filenames etc. will add a test soon

[stickler-ci]

W293 blank line contains whitespace

[djhoese]

Waiting on #647 to fix the appveyor failures, then I'll merge this.