use snackbar to tell users that H@H client is required for this feature

app/src/main/java/com/hippo/ehviewer/client/EhEngine.java

@@ -30,6 +30,7 @@ import com.hippo.ehviewer.client.data.GalleryInfo;
 import com.hippo.ehviewer.client.data.PreviewSet;
 import com.hippo.ehviewer.client.exception.CancelledException;
 import com.hippo.ehviewer.client.exception.EhException;
+import com.hippo.ehviewer.client.exception.NoHAtHClientException;
 import com.hippo.ehviewer.client.exception.ParseException;
 import com.hippo.ehviewer.client.parser.ArchiveParser;
 import com.hippo.ehviewer.client.parser.FavoritesParser;
@@ -57,6 +58,8 @@ import org.jsoup.nodes.Document;
 import java.io.File;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import okhttp3.Call;
 import okhttp3.FormBody;
@@ -79,6 +82,8 @@ public class EhEngine {
     public static final MediaType MEDIA_TYPE_JSON = MediaType.parse("application/json; charset=utf-8");
     private static final MediaType MEDIA_TYPE_JPEG = MediaType.parse("image/jpeg");
 
+    private static final Pattern PATTERN_NEED_HATH_CLIENT = Pattern.compile("(You must have a H@H client assigned to your account to use this feature\\.)");
+
     public static EhFilter sEhFilter;
 
     public static void initialize() {
@@ -665,6 +670,11 @@ public class EhEngine {
             throw e;
         }
 
+        Matcher m = PATTERN_NEED_HATH_CLIENT.matcher(body);
+        if (m.find()) {
+            throw new NoHAtHClientException("No H@H client");
+        }
+
         return null;
     }
 

app/src/main/java/com/hippo/ehviewer/client/exception/NoHAtHClientException.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2016 Hippo Seven
+ *
+ * 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.hippo.ehviewer.client.exception;
+
+public class NoHAtHClientException extends EhException {
+
+    public NoHAtHClientException(String detailMessage) {
+        super(detailMessage);
+    }
+
+}

app/src/main/java/com/hippo/ehviewer/ui/scene/GalleryDetailScene.java

@@ -74,6 +74,7 @@ import com.hippo.ehviewer.client.data.GalleryInfo;
 import com.hippo.ehviewer.client.data.GalleryTagGroup;
 import com.hippo.ehviewer.client.data.ListUrlBuilder;
 import com.hippo.ehviewer.client.data.PreviewSet;
+import com.hippo.ehviewer.client.exception.NoHAtHClientException;
 import com.hippo.ehviewer.client.parser.RateGalleryParser;
 import com.hippo.ehviewer.dao.DownloadInfo;
 import com.hippo.ehviewer.dao.Filter;
@@ -1585,7 +1586,11 @@ public class GalleryDetailScene extends BaseScene implements View.OnClickListene
 
         @Override
         public void onFailure(Exception e) {
-            showTip(R.string.download_archive_failure, LENGTH_SHORT);
+            if (e instanceof NoHAtHClientException) {
+                showTip(R.string.download_archive_failure_no_hath, LENGTH_SHORT);
+            } else {
+                showTip(R.string.download_archive_failure, LENGTH_SHORT);
+            }
         }
 
         @Override