Rename `isLegacy` to `im_legacy` for consistency and flake8 compliance
Rename `isLegacy` to `im_legacy` for consistency and flake8 compliance

beetbox/beets,ibmibmibm/beets,ibmibmibm/beets,SusannaMaria/beets,shamangeorge/beets,sampsyo/beets,shamangeorge/beets,sampsyo/beets,beetbox/beets,ibmibmibm/beets,ibmibmibm/beets,shamangeorge/beets,SusannaMaria/beets,jackwilsdon/beets,sampsyo/beets,SusannaMaria/beets,jackwilsdon/beets,jackwilsdon/beets,sampsyo/beets,SusannaMaria/beets,beetbox/beets,shamangeorge/beets,beetbox/beets,jackwilsdon/beets