Milo: Add themed page for errors

milo/appengine/buildbot/html.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package buildbot
 
 import (
         "fmt"
         "net/http"
         "os"
@@ skipping 67 matching lines @@
         return "builder.html"
 }
 
 // Render renders the buildbot builder page.
 // Note: The builder html template contains self links to "?limit=123", which could
 // potentially override any other request parameters set.
 func (b Builder) Render(c context.Context, r *http.Request, p httprouter.Params) (*templates.Args, error) {
         master := p.ByName("master")
         if master == "" {
                 return nil, &miloerror.Error{
-                        Message: "No master",
+                        Message: "No master specified",
                         Code:    http.StatusBadRequest,
                 }
         }
         builder := p.ByName("builder")
         if builder == "" {
                 return nil, &miloerror.Error{
-                        Message: "No builder",
+                        Message: "No builder specified",
                         Code:    http.StatusBadRequest,
                 }
         }
         limit, err := settings.GetLimit(r)
         if err != nil {
                 return nil, err
         }
         if limit < 0 {
                 limit = 25
         }
 
         result, err := builderImpl(c, master, builder, limit)
         if err != nil {
                 return nil, err
         }
 
         // Render into the template
         args := &templates.Args{
                 "Builder": result,
         }
         return args, nil
 }