allow prettyprinter 1.6.0 (fixes #5094)
allow prettyprinter 1.6.0 (fixes #5094)

this reverts 57062ade

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