Fix a sys.platform check in hidden test
Fix a sys.platform check in hidden test

artemutin/beets,jcoady9/beets,artemutin/beets,mosesfistos1/beetbox,beetbox/beets,ibmibmibm/beets,madmouser1/beets,jackwilsdon/beets,artemutin/beets,madmouser1/beets,MyTunesFreeMusic/privacy-policy,xsteadfastx/beets,Kraymer/beets,diego-plan9/beets,shamangeorge/beets,sampsyo/beets,beetbox/beets,Kraymer/beets,lengtche/beets,MyTunesFreeMusic/privacy-policy,ibmibmibm/beets,pkess/beets,beetbox/beets,ibmibmibm/beets,jackwilsdon/beets,jackwilsdon/beets,jcoady9/beets,pkess/beets,pkess/beets,shamangeorge/beets,MyTunesFreeMusic/privacy-policy,mosesfistos1/beetbox,SusannaMaria/beets,pkess/beets,Kraymer/beets,diego-plan9/beets,mosesfistos1/beetbox,mosesfistos1/beetbox,MyTunesFreeMusic/privacy-policy,diego-plan9/beets,SusannaMaria/beets,SusannaMaria/beets,jackwilsdon/beets,ibmibmibm/beets,Kraymer/beets,madmouser1/beets,sampsyo/beets,diego-plan9/beets,madmouser1/beets,lengtche/beets,artemutin/beets,jcoady9/beets,shamangeorge/beets,sampsyo/beets,sampsyo/beets,SusannaMaria/beets,jcoady9/beets,xsteadfastx/beets,xsteadfastx/beets,lengtche/beets,lengtche/beets,xsteadfastx/beets,shamangeorge/beets,beetbox/beets