Reliable Error State Tests - Nimbus

A test against the Nimbus library was relying on specific messaging
from Nimbus as well as the JDK, making it brittle.

Now, it simply relies on the messaging that we control.

Issue: gh-4887

oauth2/oauth2-jose/src/test/java/org/springframework/security/oauth2/jwt/NimbusJwtDecoderJwkSupportTests.java

@@ -146,7 +146,7 @@ public class NimbusJwtDecoderJwkSupportTests {
 	}
 
 	@Test
-	public void decodeWhenJwkEndpointIsUnresponsiveThenReturnsStockException() throws Exception {
+	public void decodeWhenJwkEndpointIsUnresponsiveThenRetrunsJwtException() throws Exception {
 		try ( MockWebServer server = new MockWebServer() ) {
 			server.enqueue(new MockResponse().setBody(MALFORMED_JWK_SET));
 			String jwkSetUrl = server.url("/.well-known/jwks.json").toString();
@@ -157,8 +157,7 @@ public class NimbusJwtDecoderJwkSupportTests {
 
 			assertThatCode(() -> decoder.decode(SIGNED_JWT))
 					.isInstanceOf(JwtException.class)
-					.hasMessage("An error occurred while attempting to decode the Jwt: " +
-							"Couldn't retrieve remote JWK set: Connection refused (Connection refused)");
+					.hasMessageContaining("An error occurred while attempting to decode the Jwt");
 		}
 	}
 }