Warning, treated as error:
/Users/dstansby/matplotlib/doc/examples/pylab_examples/agg_buffer.rst:8: WARNING: Exception occurred in plotting agg_buffer
 from /Users/dstansby/matplotlib/doc/mpl_examples/pylab_examples/agg_buffer.py:
Traceback (most recent call last):
  File "<string>", line 13, in <module>
ImportError: No module named 'PIL'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/dstansby/matplotlib/lib/matplotlib/sphinxext/plot_directive.py", line 525, in run_code
    six.exec_(code, ns)
  File "<string>", line 15, in <module>
SystemExit: Pillow must be installed to run this example

Building HTML failed.