add error when removing item not exists

queue/builtin/queue.go

@@ -1,11 +1,14 @@
 package builtin
 
 import (
+	"errors"
 	"sync"
 
 	"github.com/drone/drone/queue"
 )
 
+var ErrNotFound = errors.New("work item not found")
+
 type Queue struct {
 	sync.Mutex
 
@@ -40,7 +43,7 @@ func (q *Queue) Remove(work *queue.Work) error {
 
 	_, ok := q.items[work]
 	if !ok {
-		return nil
+		return ErrNotFound
 	}
 	var items []*queue.Work
 

queue/builtin/queue_test.go

@@ -34,6 +34,7 @@ func TestBuild(t *testing.T) {
 			g.Assert(len(q.itemc)).Equal(2)
 			g.Assert(q.Pull()).Equal(w1)
 			g.Assert(q.Pull()).Equal(w3)
+			g.Assert(q.Remove(w2)).Equal(ErrNotFound)
 		})
 
 		g.It("Should pull item", func() {