Re-set error for google cloud tokens

eclipse-cbi#594

webservice/signing/windows/src/main/java/org/eclipse/cbi/webservice/signing/windows/JSigner.java

@@ -114,7 +114,7 @@ private String googleAccessToken() {
 				throw new RuntimeException(ex);
 			}
 		} else {
-			return "NONE";
+			throw new RuntimeException("Tried to retrieve a Google Cloud Access Token while no credentials have been provided");
 		}
 	}