Recognize DARTS_CONFIGURE_MATPLOTLIB=0

[zgana]

Fixes #892.

Summary

This PR makes it possible to import darts without changing the global matplotlib configuration.

• By default, darts still applies matplotlib configurations
• If the environment variable DARTS_CONFIGURE_MATPLOTLIB=0 is set, then darts.u8plots_mplstyle is still defined but not applied.

Other Information

Normally it would be best to add tests of the new behavior, but it's difficult to test behavior in the root __init__.py. Both the pre-existing behavior and the adjustment here would be easier to test if the plotting configuration were factored out into some helper module. That would be a larger (though still fairly small) change.

A larger question would be: should darts change the global matplotlib configuration by default? Making this opt-in would obviously cause an aesthetic mismatch for anyone following documentation produced prior to that change. But it would arguably be cleaner (and more testable) to require e.g. darts.apply_u8plots_mplstyle() or otherwise respect users' matplotlibrc.

[hrzn]

Thanks for this, LGTM.
I agree with your comment that opting-in using something along the lines of darts.apply_u8plots_mplstyle() would be better eventually. Modifying the global config is not great. We could modify TimeSeries.plot() in order to still apply some style in those plots only, maybe.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.70%. Comparing base (e3f3309) to head (02aaad5).
Report is 492 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #924   +/-   ##
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  Coverage   91.70%   91.70%           
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  Files          74       74           
  Lines        7402     7404    +2     
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+ Hits         6788     6790    +2     
  Misses        614      614           

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[zgana]

Thanks @hrzn! I just realized I did not add an entry to the change log. Should I push another commit with an entry under "Unreleased"?

[hrzn]

Yes that'd be great - thanks!

[hrzn]

Thank you @zgana, merging now, it will be part of the next release :)