hugolib: Use Page Kind in template errors to prevent log spam

Having the content page name in the log key for the distinct error logger isnt't very usable when you have an error in a commonly used partial.

Using the Page Kind reduces the amount of log entries. Here is an example from an error in the partial menu.html, used in all the page templates:

```
Started building sites ...
ERROR 2017/04/02 12:19:43 Error while rendering "page": template: /Users/bep/sites/bepsays.com/layouts/_default/single.html:17:7: executing "/Users/bep/sites/bepsays.com/layouts/_default/single.html" at <partial "menu.html" ...>: error calling partial: template: partials/menu.html:9:11: executing "partials/menu.html" at <.DoesNotExist>: can't evaluate field DoesNotExist in type *hugolib.PageOutput
ERROR 2017/04/02 12:19:43 Error while rendering "section": template: /Users/bep/sites/bepsays.com/layouts/_default/section.html:17:7: executing "/Users/bep/sites/bepsays.com/layouts/_default/section.html" at <partial "menu.html" ...>: error calling partial: template: partials/menu.html:9:11: executing "partials/menu.html" at <.DoesNotExist>: can't evaluate field DoesNotExist in type *hugolib.PageOutput
ERROR 2017/04/02 12:19:43 Error while rendering "taxonomy": template: /Users/bep/sites/bepsays.com/layouts/_default/list.html:17:7: executing "/Users/bep/sites/bepsays.com/layouts/_default/list.html" at <partial "menu.html" ...>: error calling partial: template: partials/menu.html:9:11: executing "partials/menu.html" at <.DoesNotExist>: can't evaluate field DoesNotExist in type *hugolib.PageOutput
ERROR 2017/04/02 12:19:43 Error while rendering "home": template: /Users/bep/sites/bepsays.com/layouts/index.html:17:7: executing "/Users/bep/sites/bepsays.com/layouts/index.html" at <partial "menu.html" ...>: error calling partial: template: partials/menu.html:9:11: executing "partials/menu.html" at <.DoesNotExist>: can't evaluate field DoesNotExist in type *hugolib.PageOutput
ERROR 2017/04/02 12:19:43 Error while rendering "404": template: 404.html:2:3: executing "404.html" at <partial "menu.html" ...>: error calling partial: template: partials/menu.html:9:11: executing "partials/menu.html" at <.DoesNotExist>: can't evaluate field DoesNotExist in type *hugolib.PageOutput
Built site for language nn:
```
Which is pretty good.

hugolib/site.go

@@ -52,11 +52,6 @@ var testMode bool
 
 var defaultTimer *nitro.B
 
-var (
-	distinctErrorLogger    = helpers.NewDistinctErrorLogger()
-	distinctFeedbackLogger = helpers.NewDistinctFeedbackLogger()
-)
-
 // Site contains all the information relevant for constructing a static
 // site.  The basic flow of information is as follows:
 //
@@ -1834,11 +1829,11 @@ func (s *Site) renderAndWriteXML(name string, dest string, d interface{}, layout
 
 }
 
-func (s *Site) renderAndWritePage(name string, dest string, d interface{}, layouts ...string) error {
+func (s *Site) renderAndWritePage(name string, dest string, p *PageOutput, layouts ...string) error {
 	renderBuffer := bp.GetBuffer()
 	defer bp.PutBuffer(renderBuffer)
 
-	err := s.renderForLayouts(name, d, renderBuffer, layouts...)
+	err := s.renderForLayouts(p.Kind, p, renderBuffer, layouts...)
 
 	if err != nil {
 		return err
@@ -1858,7 +1853,7 @@ func (s *Site) renderAndWritePage(name string, dest string, d interface{}, layou
 	}
 
 	// For performance reasons we only inject the Hugo generator tag on the home page.
-	if n, ok := d.(*PageOutput); ok && n.IsHome() {
+	if p.IsHome() {
 		if !s.Cfg.GetBool("disableHugoGeneratorInject") {
 			transformLinks = append(transformLinks, transform.HugoGeneratorInject)
 		}
@@ -1887,7 +1882,7 @@ func (s *Site) renderAndWritePage(name string, dest string, d interface{}, layou
 			if !s.Cfg.GetBool("verbose") {
 				debugAddend = "* For more debugging information, run \"hugo -v\""
 			}
-			distinctFeedbackLogger.Printf(`=============================================================
+			helpers.DistinctFeedbackLog.Printf(`=============================================================
 Your rendered home page is blank: /index.html is zero-length
  * Did you specify a theme on the command-line or in your
    %q file?  (Current theme: %q)
@@ -1913,15 +1908,15 @@ Your rendered home page is blank: /index.html is zero-length
 func (s *Site) renderForLayouts(name string, d interface{}, w io.Writer, layouts ...string) error {
 	templ := s.findFirstTemplate(layouts...)
 	if templ == nil {
-		s.Log.WARN.Printf("[%s] Unable to locate layout for %s: %s\n", s.Language.Lang, name, layouts)
+		helpers.DistinctWarnLog.Printf("[%s] Unable to locate layout for %s: %s\n", s.Language.Lang, name, layouts)
 
 		return nil
 	}
 
 	if err := templ.Execute(w, d); err != nil {
 
 		// Behavior here should be dependent on if running in server or watch mode.
-		distinctErrorLogger.Printf("Error while rendering %q: %s", name, err)
+		helpers.DistinctErrorLog.Printf("Error while rendering %q: %s", name, err)
 		if !s.running() && !testMode {
 			// TODO(bep) check if this can be propagated
 			os.Exit(-1)

hugolib/site_render.go

@@ -19,6 +19,8 @@ import (
 	"sync"
 	"time"
 
+	"github.com/spf13/hugo/output"
+
 	bp "github.com/spf13/hugo/bufferpool"
 )
 
@@ -248,7 +250,12 @@ func (s *Site) render404() error {
 
 	nfLayouts := []string{"404.html"}
 
-	return s.renderAndWritePage("404 page", "404.html", p, s.appendThemeTemplates(nfLayouts)...)
+	pageOutput, err := newPageOutput(p, false, output.HTMLFormat)
+	if err != nil {
+		return err
+	}
+
+	return s.renderAndWritePage("404 page", "404.html", pageOutput, s.appendThemeTemplates(nfLayouts)...)
 
 }