src/PicoAuthPlugin.php
public function setRequestUrl($url)
    {
        $this->requestUrl = $url;
        $this->requestFile = $this->pico->resolveFilePath($url);
    }
public function setRequestUrl($url)
    {
        $this->requestUrl = $url;
        $this->requestFile = $this->pico->resolveFilePath($url);
    }
{@inheritdoc}

Will not take effect if invoked after onRequestFile Pico event.
After that, the file is already read by Pico.