bytestringify tmpdir in convert plugin
bytestringify tmpdir in convert plugin

This works fine in py 3.5, but not 3.4

xsteadfastx/beets,madmouser1/beets,artemutin/beets,pkess/beets,artemutin/beets,ibmibmibm/beets,pkess/beets,jackwilsdon/beets,SusannaMaria/beets,lengtche/beets,xsteadfastx/beets,beetbox/beets,diego-plan9/beets,lengtche/beets,MyTunesFreeMusic/privacy-policy,ibmibmibm/beets,shamangeorge/beets,pkess/beets,diego-plan9/beets,diego-plan9/beets,Kraymer/beets,diego-plan9/beets,mosesfistos1/beetbox,mosesfistos1/beetbox,artemutin/beets,lengtche/beets,SusannaMaria/beets,SusannaMaria/beets,MyTunesFreeMusic/privacy-policy,Kraymer/beets,shamangeorge/beets,artemutin/beets,madmouser1/beets,mosesfistos1/beetbox,sampsyo/beets,SusannaMaria/beets,sampsyo/beets,Kraymer/beets,jackwilsdon/beets,MyTunesFreeMusic/privacy-policy,lengtche/beets,beetbox/beets,shamangeorge/beets,pkess/beets,mosesfistos1/beetbox,beetbox/beets,ibmibmibm/beets,sampsyo/beets,shamangeorge/beets,madmouser1/beets,MyTunesFreeMusic/privacy-policy,jackwilsdon/beets,jackwilsdon/beets,xsteadfastx/beets,ibmibmibm/beets,xsteadfastx/beets,madmouser1/beets,Kraymer/beets,beetbox/beets,sampsyo/beets