Add error message for authlib-injector download failure

HMCLCore/src/main/java/org/jackhuang/hmcl/auth/authlibinjector/AuthlibInjectorAccount.java

@@ -69,7 +69,7 @@ public class AuthlibInjectorAccount extends YggdrasilAccount {
             try {
                 return authlibInjectorDownloader.get();
             } catch (IOException e) {
-                throw new CompletionException(new AuthenticationException("Failed to download authlib-injector", e));
+                throw new CompletionException(new AuthlibInjectorDownloadException(e));
             }
         });
 

HMCLCore/src/main/java/org/jackhuang/hmcl/auth/authlibinjector/AuthlibInjectorDownloadException.java

@@ -0,0 +1,41 @@
+/*
+ * Hello Minecraft! Launcher.
+ * Copyright (C) 2018  huangyuhui <huanghongxun2008@126.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see {http://www.gnu.org/licenses/}.
+ */
+package org.jackhuang.hmcl.auth.authlibinjector;
+
+import org.jackhuang.hmcl.auth.AuthenticationException;
+
+/**
+ * @author yushijinhun
+ */
+public class AuthlibInjectorDownloadException extends AuthenticationException {
+
+    public AuthlibInjectorDownloadException() {
+    }
+
+    public AuthlibInjectorDownloadException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public AuthlibInjectorDownloadException(String message) {
+        super(message);
+    }
+
+    public AuthlibInjectorDownloadException(Throwable cause) {
+        super(cause);
+    }
+}