Deprecate GraphicsArray import from sage.plot.graphics

[egourgoulhon]

#27865 has refactored the class GraphicsArray, making it a subclass of MultiGraphics, and has moved its definition from src/sage/plot/graphics.py to src/sage/plot/multigraphics.py. As pointed out in ​https://groups.google.com/d/msg/sage-devel/eTl4DHcwnOo/uQSOtstWAwAJ, this has broken Sage's API: the import via

from sage.plot.graphics import GraphicsArray

does not longer work. This ticket makes it work again, but with the following deprecation notice:

DeprecationWarning: GraphicsArray must be imported from sage.plot.multigraphics 
and no longer from sage.plot.graphics.
See https://trac.sagemath.org/28675 for details.

A possible shortcoming of the approach adopted here is that the deprecation message appears only at the first use of GraphicsArray, not during the import itself. Actually, I don't know if it is possible to generate a deprecation warning during some import.

[egourgoulhon]

New commits:

​e16951e

Deprecation notice for GraphicsArray import from sage.plot.graphics

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​87bc58a

Fix merge conflict of #28675 branch with Sage 9.0.beta4

[egourgoulhon]

The merge conflict solved above was due to the introduction of #27866 in Sage 9.0.beta4.

[kcrisman]

I like the spirit of this. Can you actually view this array and do the usual (old) methods with it for now? (I regret that I cannot actually test this due to time constraints - a sad refrain the past few years.) Anyway, if so and green patchbot, this is probably the best way to deal with this situation, unless William has other improvements he would suggest.

[egourgoulhon]

Replying to kcrisman:

I like the spirit of this. Can you actually view this array and do the usual (old) methods with it for now?

Yes absolutely, since the object constructed from sage.plot.graphics.GraphicsArray is actually a sage.plot.multigraphics.GraphicsArray.

[egourgoulhon]

Replying to kcrisman:

Anyway, if so and green patchbot, this is probably the best way to deal with this situation, unless William has other improvements he would suggest.

The patchbot is still green...

[egourgoulhon]

Thanks!

[kcrisman]

+1 thanks chapoton!