title: imagick readImageBlob giving 'uable to open file' error
body: <p>I am getting the following error:</p>
  
  <p>PHP Fatal error:  Uncaught exception 'ImagickException' with message 'unable to open image `/tmp/magick-2244K7gyKdSJDqKW': No such file or directory @ error/blob.c/OpenBlob/2658' in /var/www/nodeviz-read-only/www/NodeViz/library/GraphVizExporter.php:454</p>
  
  <p>The relevant code referenced is here:</p>
  
  <pre><code>    $im = new Imagick();
      $im-&gt;setFormat('svg');
      #remove labels from the raster version
      $im-&gt;readImageBlob(preg_replace('/&lt;text.+\/text&gt;/m', "", $this-&gt;svgString));
  </code></pre>
  
  <p>I'm not sure where to look to start debugging this. Any suggestions as to what could be causing this error would be appreciated. (I didn't write code, I'm just trying to use it.)</p>