Show proper error message if registering email address fails

Users can register new email address under 'Settings > Contact
Information'. If the registration fails, e.g. because the mail server
is incorrectly configured or because the mail server refuses to send
the email, an error dialog with 'Code Review - Error > Server Error >
[message]' is displayed which makes the user think that there is
something wrong with Gerrit. Slightly improve the error reporting by
setting a proper title for the error dialog and removing 'Server Error'
from the message.

Bug: issue 1480
Change-Id: I788e5bdf69aaaee17a1fd468f81d3effaa13a624
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

gerrit-common/src/main/java/com/google/gerrit/common/errors/EmailException.java

@@ -0,0 +1,29 @@
+// Copyright (C) 2009 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.common.errors;
+
+public class EmailException extends Exception {
+  private static final long serialVersionUID = 1L;
+
+  public static final String MESSAGE = "Mail Error: ";
+
+  public EmailException(String msg) {
+    super(MESSAGE + msg);
+  }
+
+  public EmailException(String msg, Throwable why) {
+    super(MESSAGE + msg, why);
+  }
+}