Bug#966712: statsmodels: debci tests fail

[Rebecca N. Palmer]

Control: severity -1 serious
Control: tags -1 fixed-upstream patch

test_full_output*:
https://github.com/statsmodels/statsmodels/issues/6771
test_plot:
https://github.com/statsmodels/statsmodels/commit/fa8739e9d2822fe985bc96cd31bb3eb568fd9dc7