matplotlib/matplotlib — pull request #1537 by mdboom (2012-11-27 15:32:16+00:00)
Title: Fix savefig.extension == "auto"

`savefig.extension` was deprecated and replaced with `savefig.format`. However, `savefig.extension` supported "auto" as a value, which the user may still have in their matplotlibrc. When converting it over to `savefig.format`, the "auto" value should be converted to "png".