fix legend w/ 'expand' mode which fails for a single item.

[leejjoon]

The problem is originally reported in the mailing list.

http://matplotlib.1069221.n5.nabble.com/Trouble-with-legend-and-axis-scaling-tp40745.html

Basically, the legend "expand" mode fails when there is one item to show.
The PR fixes this problem.

[leejjoon]

As a workaround for a current versions, one may add an invisible item. For example,

handles, labels = ax.get_legend_handles_labels()
if len(handles) == 1:
   from matplotlib.patches import Circle
   handles.append(Circle((0,0), 1, visible=False))
   labels.append("")
   plt.legend(handles, labels,
              bbox_to_anchor=(0., 1.02, 1., 0.102), loc=3, mode='expand',
              numpoints=1, ncol=2, borderaxespad=0.)

[pelson]

Thanks @leejjoon this looks 👍

Is it easy to add/update a test for this?

[frixhax]

Thanks, that worked for me!

[pelson]

Is it easy to add/update a test for this?

Bump. I'm happy to merge this, but it'd be even better if we had a test to ensure we don't digress in the future.

Thanks @leejjoon

[pelson]

Thanks @leejjoon & @dmcdougall!