DRY fix: reuse BS3_BREAKPOINT_KEYS
DRY fix: reuse BS3_BREAKPOINT_KEYS

haricot/djangocms-bs4forcascade,haricot/djangocms-bs4forcascade,rfleschenberg/djangocms-cascade,rfleschenberg/djangocms-cascade,jrief/djangocms-cascade,jrief/djangocms-cascade,jrief/djangocms-cascade,rfleschenberg/djangocms-cascade