Fix DeprecationWarning in stackplot.py

[sjpfenninger]

In matplotlib 1.5.0, plt.stackplot() raises a DeprecationWarning ("The set_color_cycle attribute was deprecated in version 1.5. Use set_prop_cycle instead"):

The simple replacement in the attached pull request seems to fix this.

[mdboom]

👍

[tacaswell]

👍 seems reasonable enough to me.

[tacaswell]

It seems that stackplot is in need of a re-write, but that is way outside of the scope of this PR.

[WeatherGod]

Holy crap! I didn't notice that this function modified the axes's cycle! This change should probably also reset the property cycle to its default prior to returning if it modified it originally.

What I also don't like is that this uses the cycler in a bad way. Specifying the colors shouldn't do anything to the property cycle at all. Maybe the refactor of cycle handling will help here?

[mdboom]

@WeatherGod: I hear you on all this. I think for 1.5.x we can just do exactly this PR (to simply silence the warning). Anything else is probably best done on 2.0.x or later.

[WeatherGod]

Agreed. Sorry if I wasn't clear. v1.5 should duplicate the current behavior.

[sjpfenninger]

Yeah, my aim was just to silence the warning, I didn't look at the bigger picture at all..

[tacaswell]

backported to v1.5.x as ba9ee86

[tacaswell]

@sjpfenninger Thank you and congratulations on (what I think is) your first mpl contribution!