'AxesSubplot' object has no attribute 'set_axis_bgcolor'

[jnothman]

It seems one of our examples, examples/covariance/plot_sparse_cov.py, makes use of a method from Matplotlib that has been removed in the latest release (2.2.0). CircleCI logs show:

/home/circleci/project/examples/covariance/plot_sparse_cov.py failed leaving traceback:
Traceback (most recent call last):
  File "/home/circleci/project/examples/covariance/plot_sparse_cov.py", line 124, in <module>
    ax.set_axis_bgcolor('.7')
AttributeError: 'AxesSubplot' object has no attribute 'set_axis_bgcolor'

We need to use an alternative.

[jnothman]

It looks like set_axis_bgcolor was replaced by set_facecolor

[iArunava]

On this! I will submit a PR right away!