update INSTALL for qt5

INSTALL

@@ -10,7 +10,7 @@ you have to handle them by hand, according to your distribution.
 The requirements are provided in ``setup.py``, except for:
 
 * gpgv (for secure updates). If not packaged alone, it should be in ``gnupg`` or ``gpg``.
-* PyQt4 (python-qt4) for graphical applications.
+* PyQt5 (python-pyqt5, pyqt5-dev-tools, python-pyqt5.qtmultimedia) for graphical applications.
 * For more performance, ensure you have ``libyaml`` and ``simplejson`` installed.
 
 Some modules may have more dependencies.