Fail the grants table test for any row whose user is not composed, so a row can never pass for a missing user (issue 1955)

go/buscompose/buscompose_test.go

@@ -800,9 +800,12 @@ func healthChecks(t *testing.T) {
 			}
 		}
 	}
-	for name := range mayNot {
-		if !seen[name] {
-			t.Errorf("no user %s was composed", name)
+	// Every row names a user that was composed, in either table: a row for a user absent would pass for nothing.
+	for _, table := range []map[string][]string{may, mayNot} {
+		for name := range table {
+			if !seen[name] {
+				t.Errorf("no user %s was composed", name)
+			}
 		}
 	}
 }