Bug? cant copy file /tmp/phpBlablabla

League\Flysystem\FileNotFoundException
File not found at path: tmp/phpkiLfKz

```
public function copy($path, $newpath)
    {
        $path = Util::normalizePath($path);  // <-- bug here
        $newpath = Util::normalizePath($newpath);
        $this->assertPresent($path);
        $this->assertAbsent($newpath);

        return $this->getAdapter()->copy($path, $newpath);
    }
```
