Issue 1:
Bug report

In tag 2.0.1 the NavigationToolbar2QT includes an unchecked call to a Qt5 feature:

pm.setDevicePixelRatio(self.canvas._dpi_ratio)

https://github.com/matplotlib/matplotlib/blob/v2.0.1/lib/matplotlib/backends/backend_qt5.py#L587-L592

This is strange, b/c it's not there in tag 2.0.0 and it's not there in master!

I can reproduce this with a simple plt.plot(np.random.randn(10)).

AttributeError: 'PySide.QtGui.QPixmap' object has no attribute 'setDevicePixelRatio'

Issue goes away when I revert to 2.0.0

Issue 2:
Bug report

Bug summary

Running arbitrary tests with matplotlib-2.0.1 results in

AttributeError: 'QPixmap' object has no attribute 'setDevicePixelRatio'

matplotlib-2.0.0 works fine

Arbitrary test, f.i.
python histogram_demo_cumulative.py

**Actual outcome**

<!--The output produced by the above code, which may be a screenshot, console output, etc.-->

If applicable, paste the console output here

`Traceback (most recent call last):

File "histogram_demo_cumulative.py", line 16, in

histtype='step', cumulative=True)

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/pyplot.py", line 3066, in hist

ax = gca()

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/pyplot.py", line 950, in gca

return gcf().gca(**kwargs)

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/pyplot.py", line 586, in gcf

return figure()

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/pyplot.py", line 535, in figure

**kwargs)

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_qt4agg.py", line 46, in new_figure_manager

return new_figure_manager_given_figure(num, thisFig)

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_qt4agg.py", line 54, in new_figure_manager_given_figure

return FigureManagerQT(canvas, num)

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_qt5.py", line 488, in init

self.toolbar = self._get_toolbar(self.canvas, self.window)

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_qt5.py", line 539, in _get_toolbar

toolbar = NavigationToolbar2QT(canvas, parent, False)

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_qt5.py", line 585, in init

NavigationToolbar2.init(self, canvas)

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/backend_bases.py", line 2760, in init

self._init_toolbar()

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_qt5.py", line 601, in _init_toolbar

a = self.addAction(self._icon(image_file + '.png'),

File "/usr/local/lib/python2.7/site-packages/matplotlib-2.0.1-py2.7-linux-x86_64.egg/matplotlib/backends/backend_qt5.py", line 591, in _icon

pm.setDevicePixelRatio(self.canvas._dpi_ratio)

AttributeError: 'QPixmap' object has no attribute 'setDevicePixelRatio'

Expected outcome

Matplotlib version

Operating System: Linux

Matplotlib Version: 2.0.1

Python Version: 2.7.13

Jupyter Version (if applicable):

Other Libraries:

Installed from source