Try to fix the failing Prettier test.

Author: nedtwigg

testlib/src/test/java/com/diffplug/spotless/npm/PrettierFormatterStepTest.java

@@ -111,8 +111,8 @@ void verifyPrettierErrorMessageIsRelayed() throws Exception {
 					npmPathResolver(),
 					new PrettierConfig(null, ImmutableMap.of("parser", "postcss")));
 			try (StepHarnessWithFile stepHarness = StepHarnessWithFile.forStep(this, formatterStep)) {
-				stepHarness.testResourceExceptionMsg("npm/prettier/filetypes/scss/scss.dirty").startsWith(
-						"com.diffplug.spotless.npm.SimpleRestClient$SimpleRestResponseException: Unexpected response status code at /prettier/format [HTTP 501] -- (Error while formatting: Error: Couldn't resolve parser \"postcss\")");
+				stepHarness.testResourceExceptionMsg("npm/prettier/filetypes/scss/scss.dirty").isEqualTo(
+						"Unexpected response status code at /prettier/format [HTTP 501] -- (Error while formatting: Error: Couldn't resolve parser \"postcss\")");
 			}
 		}
 	}