I'm using Python 3.5.1 (Anaconda 2.5.0 distribution) on OS X 10.11.3. With Matplotlib 1.5.1, when I tried to import pyplot (e.g., import matplotlib.pyplot as pl), I would get the following error:

2016-03-29 19:00:39.396 python[30241:4673155] ApplePersistenceIgnoreState: Existing state will not be touched. New state will be written to /var/folders/vm/851b53f57ql7tsx_jjpltblh0000gn/T/com.continuum.python.savedState

I would get the same error if I tried to use the --pylab flag when I started IPython or if I used the %pylab magic. After import matplotlib.pyplot as pl, I could go ahead and use, e.g., pl.plot to make a figure, but once the figure showed up, it wouldn't return control to IPython.

So, I removed Matplotlib 1.5.1 and installed 1.4, and the problem seemed to go away. But then I got the same error message the first time I tried to plot something. In this case, it showed the figure just fine, and it returns control to IPython just fine. However, when a figure doesn't show up and I use, e.g., pl.show(), it (still) doesn't return control.