TEST: Merge pull request #6442 from matthew-brett/dynamic-tkagg#6474

efiring wants to merge 1 commit intomatplotlib:v1.5.xmatplotlib/matplotlib:v1.5.xfrom

efiring:backport_tk_to_v1.5.xefiring/matplotlib:backport_tk_to_v1.5.xCopy head branch name to clipboard