Right-Click menu on a pushButton doesn't show up

[qtpyqt]

Hi,

I'm trying to add a right-click menu on a pushButton, but the menu doesn't show up??
Anyone to help?

def addChannelsMenu(self):
            chmenu = QtGui.QMenu()
            chmenu.addAction('testing')
            chmenu.addAction('testing1')
            chmenu.addSeparator()
            chmenu.addAction('testing2')
            #self.channelsBtn.setMenu(chmenu)
 
            #self.channelsBtn.showMenu()
            self.zoomBtn.setMenu(chmenu)

def addChannelsMenu(self):
            chmenu = QtGui.QMenu()
            chmenu.addAction('testing')
            chmenu.addAction('testing1')
            chmenu.addSeparator()
            chmenu.addAction('testing2')
            #self.channelsBtn.setMenu(chmenu)
            
            #self.channelsBtn.showMenu()
            self.zoomBtn.setMenu(chmenu)

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I tried repainting but it wouldn't help either:

self.zoomBtn.repaint()

self.zoomBtn.repaint()

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I'm on Fedora8 at the moment.