matplotlib is not in install_requires but necessary for some imports

[MartinBubel]

matplotlib is not part of the install_requires list in the setup.py file but some imports, e.g.

from GPy.models.gp_coregionalized_regression import GPCoregionalizedRegression as CO

import GPy.plotting which imports matplotlib, resulting in errors.

This is not something we need to consider asap but for sure something to fix soon.

[MartinBubel]

will be adressed under #1080

[apaleyes]

A few additional observations here.

First, this line forces import of mpl immediately when one imports GPy, and that is probably not a wanted behaviour:

GPy/GPy/__init__.py

Line 16 in aa49220

from . import plotting

Second, GPy[plotting] hardcodes a very specific version of mpl that cannot be installed at least on windows:

GPy/setup.py

Line 209 in aa49220

"plotting": [matplotlib_version, "plotly >= 1.8.6"],

Could be worth addressing too!