fix test case

Author: sokra

test/Errors.test.js

@@ -350,7 +350,9 @@ describe("Errors", () => {
 			(errors, warnings) => {
 				expect(errors).toHaveLength(1);
 				const messages = errors[0].split("\n");
-				expect(messages[1]).toMatch(/^Module build failed: Final loader \(.+\) didn't return a Buffer or String/);
+				expect(messages[1]).toMatch(
+					/^Module build failed: Error: Final loader \(.+\) didn't return a Buffer or String/
+				);
 				done();
 			}
 		);