title: PyQt : Editable QFileSystemModel in a QTreeView
body: <p>I've got this on my file System :</p>
  
  <pre><code> - myFolder
        - mySubFolder
  </code></pre>
  
  <ol>
  <li>Within the TreeView I expand the folder <strong>"myFolder"</strong>.</li>
  <li>Then I rename it as <strong>"myFolder_2"</strong>.</li>
  <li>And finaly I try to rename the folder <strong>"mySubFolder"</strong> as <strong>"mySubFolder_2"</strong>.</li>
  </ol>
  
  <p><strong>"mySubFolder_2"</strong> in is no more considered as a folder but as unknown with a size of -1 bytes and I've got the message : <em>QFileSystemWatcher: failed to add paths: <strong>myFolder</em></strong>.</p>
  
  <p>Here is the my source code :</p>
  
  <pre><code>from PyQt4 import QtGui
  import sys
  
  app = QtGui.QApplication(sys.argv)
  treeView = QtGui.QTreeView()
  fileSystemModel = QtGui.QFileSystemModel(treeView)
  fileSystemModel.setReadOnly(False)
  treeView.setModel(fileSystemModel)
  folder = "."
  treeView.setRootIndex(fileSystemModel.setRootPath(folder))
  treeView.show()
  end = app.exec_()
  </code></pre>
  
  <p>Any help will be welcome.</p>