giggles can not show() on the current OSX.

[JuanaHe]

~/opt/anaconda3/lib/python3.7/site-packages/biggles/libplot/renderer.py in init(self, ll, ur, type, parameters, file)
150 self.lowerleft = ll
151 self.upperright = ur
--> 152 super(LibplotRenderer, self).init(type, parameters, filename)
153 #self.pl = raw.new( type, parameters, file )
154 #self.pl = Plotter(type, parameters, file)

RuntimeError: could not create plotter