pkg/tool/http: prevent TestTLS from being chatty

The http server would print tls errors to stderr by default:

    $ go test
    server.go:3495: http: TLS handshake error from 127.0.0.1:47098: remote error: tls: bad certificate
    PASS
    ok  	cuelang.org/go/pkg/tool/http	0.021s

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: Ic5678957d9180bc27774e256cbb2134e1d196c20
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1201509
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Roger Peppe <[email protected]>

Author: mvdan

pkg/tool/http/http_test.go

@@ -17,6 +17,8 @@ package http
 import (
 	"encoding/pem"
 	"fmt"
+	"io"
+	"log"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -30,10 +32,13 @@ import (
 )
 
 func newTLSServer() *httptest.Server {
-	server := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	server := httptest.NewUnstartedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		resp := `{"foo": "bar"}`
 		w.Write([]byte(resp))
 	}))
+	// The TLS errors produced by TestTLS would otherwise print noise to stderr.
+	server.Config.ErrorLog = log.New(io.Discard, "", 0)
+	server.StartTLS()
 	return server
 }