allow simple's testsuite to "MonadFail" (alevy/simple#23)
allow simple's testsuite to "MonadFail" (alevy/simple#23)

iand675/stackage,fimad/stackage,jonschoning/stackage,simonmichael/stackage,stackbuilders/stackage,athanclark/stackage,Daniel-Diaz/stackage,clinty/stackage,massysett/stackage,mrkkrp/stackage,fpco/stackage,michalkonecny/stackage,soenkehahn/stackage,asr/stackage,spencerjanssen/stackage