title: Qt Installer Framework: maintenancetool --checkupdates flag returns nothing
body: <p>The maintenance tool that is bundled with online installers for Qt applications can supposedly be run headlessly with a "--checkupdates" flag that returns update information if available (see <a href="https://stackoverflow.com/questions/34318934/qt-installer-framework-auto-update">Qt Installer Framework: Auto Update</a>).  Unfortunately I cannot get this command to actually return anything, even when there is a known update available.  I can start the maintenancetool from the command line and the update is visible, but trying to use the --checkupdates flag produces nothing.</p>
  
  <pre><code>QProcess update;
  update.setWorkingDirectory(QDir::currentPath());
  update.start("maintenancetool --checkupdates");
  
  // Wait until the maintenancetool is finished
  update.waitForFinished();
  
  // Read the output
  QByteArray data = update.readAllStandardOutput();
  </code></pre>
  
  <p>I can get this code to open the maintenancetool if I remove the --checkupdates flag, but data is always empty even if there is an update.  If I try and run the process in the command line it also produces nothing, so I don't think it's a problem with the code.  Any ideas?  There doesn't seem to be a lot of information out there about this.</p>