There is https://github.com/matplotlib/matplotlib/blob/master/doc-requirements.txt which has this. I guess the docs have gotten out of date?

Should have the instruction to pip install -r ../doc-requirements.txt someplace.

Also looks like the docs need graphviz to build too.

writing output... [ 58%] api/animation_api                                                                                                                                                                      
Warning, treated as error:
WARNING: dot command 'dot' cannot be run (needed for graphviz output), check the graphviz_dot setting

Building HTML failed.

Huh, odd, it definitely checked for numpydoc, ipython, and colorspacious when I started trying to build (and force stopped the build at the beginning), but not pillow or graphviz.

My bad… I forgot a couple of dependencies when I added the checks early on in the documentation build.
I'll fix that.

Pretty sure this is fixed now.

At least on OSX, graphviz is needed to build the docs, should this be added to the requirements?

reading sources... [100%] users/whats_new                                                                                                                
generating thumbnails... [100%] build/plot_directive/mpl_examples/pylab_examples/xcorr_demo.png                                                          
looking for now-outdated files... none found
pickling environment... done
checking consistency... done
preparing documents... done
writing output... [ 58%] api/animation_api                                                                                                               
Warning, treated as error:
WARNING: dot command 'dot' cannot be run (needed for graphviz output), check the graphviz_dot setting

Building HTML failed.

I didn't think graphviz was pip-installable. Is the requirement documented somewhere?

graphvis is not pip installable.

I can confirm that graphviz also seems to be required for building the docs on a GNU/Linux system (at least on Arch). I just got a nice build failure (the same as @dstansby ) after 10 min :/.

Huh, how isn't graphviz pip-installable? I just genuinely tried pip install graphviz and I was returned a kind Successfully installed graphviz-0.5.2 :). Let's see if the doc now builds. Edit: Nevermind, I did not notice that the “graphviz” from pip is simply some kind of wrapper… Sorry for the noise.

For the record, I had run pip install -r ../doc-requirements.txt before getting the error about graphviz.

https://pypi.python.org/pypi/graphviz/0.5.2

To render the generated DOT source code, you also need to install Graphviz

so I guess there's no harm in adding this to doc-requirements.txt. Is there a way to test for graphviz before running the whole doc build though?

which dot will check if the underlying binary is installed or not.

Closed in #8544 if not before.