Error handling. Vendoring

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>

vendor/github.com/go-redis/redis/internal/log.go

@@ -0,0 +1,15 @@
+package internal
+
+import (
+	"fmt"
+	"log"
+)
+
+var Logger *log.Logger
+
+func Logf(s string, args ...interface{}) {
+	if Logger == nil {
+		return
+	}
+	Logger.Output(2, fmt.Sprintf(s, args...))
+}