Adding test cases for the new .exists() method on SelectQuery
Adding test cases for the new .exists() method on SelectQuery

jnovinger/peewee,ghukill/peewee,coreos/peewee,zhang625272514/peewee,ronyb29/peewee,giserh/peewee,coreos/peewee,fuzeman/peewee,jnovinger/peewee,zhang625272514/peewee,coreos/peewee,lez/peewee,d1hotpep/peewee,Sunzhifeng/peewee,coleifer/peewee,Dipsomaniac/peewee,new-xiaji/peewee,teserak/peewee,wenxer/peewee,softside/peewee,giserh/peewee,mackjoner/peewee,bopo/peewee,bopo/peewee,Sunzhifeng/peewee,jarrahwu/peewee,Sunzhifeng/peewee,stas/peewee,coleifer/peewee,bopo/peewee,jarrahwu/peewee,Dipsomaniac/peewee,py4a/peewee,Dipsomaniac/peewee,new-xiaji/peewee,fuzeman/peewee,d1hotpep/peewee,jarrahwu/peewee,new-xiaji/peewee,zhang625272514/peewee,wenxer/peewee,coleifer/peewee