Adding more details for mutation error messages with scalar/uid type …

…mismatch (#4317)

* Adding more details for error messages with scalar/uid type mismatch

* used %q instead of "%s"

worker/mutation.go

@@ -349,10 +349,10 @@ func ValidateAndConvert(edge *pb.DirectedEdge, su *pb.SchemaUpdate) error {
 		return nil
 
 	case !schemaType.IsScalar() && storageType.IsScalar():
-		return errors.Errorf("Input for predicate %s of type uid is scalar", edge.Attr)
+		return errors.Errorf("Input for predicate %q of type uid is scalar. Edge: %v", edge.Attr, edge)
 
 	case schemaType.IsScalar() && !storageType.IsScalar():
-		return errors.Errorf("Input for predicate %s of type scalar is uid. Edge: %v", edge.Attr, edge)
+		return errors.Errorf("Input for predicate %q of type scalar is uid. Edge: %v", edge.Attr, edge)
 
 	// The suggested storage type matches the schema, OK!
 	case storageType == schemaType && schemaType != types.DefaultID: