'Make an xterm when a button is pressed.'

def xterm(self, _ignore=None):

    if ((self.selection is None) or (self.net is None) or (self.selection not in self.itemToWidget)):
        return
    name = self.itemToWidget[self.selection]['text']
    if (name not in self.net.nameToNode):
        return
    term = makeTerm(self.net.nameToNode[name], 'Host', term=self.appPrefs['terminalType'])
    if (StrictVersion(MININET_VERSION) > StrictVersion('2.0')):
        self.net.terms += term
    else:
        self.net.terms.append(term)
