mpl2.0 was OK
This is fedora 25
mpl updated via pip
python3.5.2
switch to Qt5Agg works

import numpy as np
import matplotlib.pyplot as plt
plt.plot (np.arange(10))
plt.show()

python3 ./test_mpl.py
Traceback (most recent call last):
File "./test_mpl.py", line 3, in
plt.plot (np.arange(10))
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/pyplot.py", line 3306, in plot
ax = gca()
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/pyplot.py", line 950, in gca
return gcf().gca(**kwargs)
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/pyplot.py", line 586, in gcf
return figure()
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/pyplot.py", line 535, in figure
**kwargs)
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/backends/backend_qt4agg.py", line 46, in new_figure_manager
return new_figure_manager_given_figure(num, thisFig)
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/backends/backend_qt4agg.py", line 54, in new_figure_manager_given_figure
return FigureManagerQT(canvas, num)
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/backends/backend_qt5.py", line 488, in init
self.toolbar = self._get_toolbar(self.canvas, self.window)
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/backends/backend_qt5.py", line 539, in _get_toolbar
toolbar = NavigationToolbar2QT(canvas, parent, False)
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/backends/backend_qt5.py", line 585, in init
NavigationToolbar2.init(self, canvas)
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/backend_bases.py", line 2760, in init
self._init_toolbar()
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/backends/backend_qt5.py", line 601, in _init_toolbar
a = self.addAction(self._icon(image_file + '.png'),
File "/home/nbecker/.local/lib/python3.5/site-packages/matplotlib/backends/backend_qt5.py", line 591, in _icon
pm.setDevicePixelRatio(self.canvas._dpi_ratio)
AttributeError: 'QPixmap' object has no attribute 'setDevicePixelRatio'