convert: Debug log when embedding images
convert: Debug log when embedding images

To help diagnose #1671.

LordSputnik/beets,madmouser1/beets,kareemallen/beets,diego-plan9/beets,MyTunesFreeMusic/privacy-policy,pkess/beets,mosesfistos1/beetbox,m-urban/beets,mried/beets,kareemallen/beets,kelvinhammond/beets,parapente/beets,shamangeorge/beets,jackwilsdon/beets,ibmibmibm/beets,beetbox/beets,Kraymer/beets,m-urban/beets,Freso/beets,shamangeorge/beets,madmouser1/beets,xsteadfastx/beets,shamangeorge/beets,pkess/beets,m-urban/beets,diego-plan9/beets,kelvinhammond/beets,Kraymer/beets,jcoady9/beets,diego-plan9/beets,madmouser1/beets,swt30/beets,jmwatte/beets,SusannaMaria/beets,beetbox/beets,swt30/beets,ibmibmibm/beets,shamangeorge/beets,mosesfistos1/beetbox,mried/beets,jcoady9/beets,LordSputnik/beets,jmwatte/beets,Freso/beets,mried/beets,beetbox/beets,parapente/beets,LordSputnik/beets,jcoady9/beets,artemutin/beets,jmwatte/beets,m-urban/beets,jmwatte/beets,xsteadfastx/beets,artemutin/beets,SusannaMaria/beets,Freso/beets,lengtche/beets,parapente/beets,SusannaMaria/beets,Kraymer/beets,jackwilsdon/beets,beetbox/beets,lengtche/beets,artemutin/beets,lengtche/beets,ibmibmibm/beets,kareemallen/beets,madmouser1/beets,diego-plan9/beets,MyTunesFreeMusic/privacy-policy,SusannaMaria/beets,mosesfistos1/beetbox,pkess/beets,swt30/beets,MyTunesFreeMusic/privacy-policy,sampsyo/beets,jackwilsdon/beets,artemutin/beets,jackwilsdon/beets,MyTunesFreeMusic/privacy-policy,mosesfistos1/beetbox,ibmibmibm/beets,xsteadfastx/beets,kareemallen/beets,swt30/beets,Kraymer/beets,jcoady9/beets,kelvinhammond/beets,Freso/beets,sampsyo/beets,parapente/beets,LordSputnik/beets,kelvinhammond/beets,mried/beets,sampsyo/beets,xsteadfastx/beets,lengtche/beets,sampsyo/beets,pkess/beets