+ button on Slice list view redirects to Table view with alert

caravel/templates/caravel/add_slice.html

@@ -0,0 +1,4 @@
+<script>
+  var msg = "Click on a table link to create a Slice";
+  window.location = "/r/msg/?url={{ '/tablemodelview/list/' }}&msg=" + msg;
+</script>

caravel/views.py

@@ -223,6 +223,7 @@ if config['DRUID_IS_ACTIVE']:
 
 class SliceModelView(CaravelModelView, DeleteMixin):  # noqa
     datamodel = SQLAInterface(models.Slice)
+    add_template = "caravel/add_slice.html"
     can_add = False
     label_columns = {
         'created_by_': 'Creator',
@@ -405,6 +406,12 @@ class R(BaseView):
         return("{request.headers[Host]}/r/{obj.id}".format(
             request=request, obj=obj))
 
+    @expose("/msg/")
+    def msg(self):
+        """Redirects to specified url while flash a message"""
+        flash(request.args.get("msg"), "info")
+        return redirect(request.args.get("url"))
+
 appbuilder.add_view_no_menu(R)