func (l *logger) Create(name string) (afero.File, error) {
	ret, err := l.backend.Create(name)
	l.logf("Create(%s) %v", name, err)
	return ret, err
}
Create creates a file in the filesystem, returning the file and an
error, if any happens.
package logger
import (
	"fmt"
	"io"
	"os"
	"time"
	"github.com/spf13/afero"
)
type logger struct {
	w       io.Writer
	backend afero.Fs
}
func New(w io.Writer, fs afero.Fs) afero.Fs {
	return &logger{
		w:       w,
		backend: fs,
	}
}
func (l *logger) logf(fmtstr string, args ...interface{}) {
	fmtstr = fmt.Sprintf("[%s] %s\n", l.backend.Name(), fmtstr)
	fmt.Fprintf(l.w, fmtstr, args...)
}