I pushed a simple fix for the CircleCI problem with jessie (circleci/python3.6 uses Debian stretch rather than Debian jessie and should get rid of the problem):

W: Failed to fetch http://deb.debian.org/debian/dists/jessie-updates/main/binary-amd64/Packages  404  Not Found

Running ag -i "plt.figure\(\w+\)" examples on ad6a28b returns:

examples/ensemble/plot_feature_transformation.py
94:plt.figure(1)
107:plt.figure(2)

examples/cluster/plot_affinity_propagation.py
49:plt.figure(1)

examples/cluster/plot_color_quantization.py
85:plt.figure(1)
91:plt.figure(2)
97:plt.figure(3)

examples/cluster/plot_adjusted_for_chance_measures.py
74:plt.figure(1)
104:plt.figure(2)

examples/cluster/plot_kmeans_digits.py
108:plt.figure(1)

examples/cluster/plot_mean_shift.py
45:plt.figure(1)

examples/gaussian_process/plot_gpc_isoprobability.py
67:fig = plt.figure(1)

examples/linear_model/plot_lasso_coordinate_descent_path.py
49:plt.figure(1)
64:plt.figure(2)
77:plt.figure(3)

examples/feature_selection/plot_feature_selection.py
43:plt.figure(1)

examples/manifold/plot_mds.py
61:fig = plt.figure(1)

examples/exercises/plot_iris_exercise.py
42:    plt.figure(fig_num)

examples/applications/plot_outlier_detection_housing.py
80:    plt.figure(1)
86:    plt.figure(2)
97:plt.figure(1)  # two clusters
119:plt.figure(2)  # "banana" shape

curious, how did you find which fonts it needs?

Could you please also do a [doc build] commit to check the complete build?

@thomasjpfan basically the problem with sphinx-gallery 0.3.1 only appears when your use figure numbers that don't match the default matplotlib figure numbering (i.e. 1, 2, 3, ..., n_figures). So I only fixed the examples with non-default matplotlib numbering (I even cheated intially and did git grep 000.png to find the included images that were starting at 000.png rather than 001.png). After that I did look at git grep -P 'plt.figure\(.+\)' to figure out which additional examples were problematic.

@adrinjalali I used docker with the circleci/python3.6 image locally to quickly debug. I then guessed by trial and error + googling. Luckily (or unluckily it depends) I had a similar convert error recently on my computer (for some reasons /etc/ImageMagick-6/policy.xml was disabling PS conversions ...). FYI in both cases the problematic image was doc/images/iris.svg (my understanding is that sphinx converts it to a png during the build).

I pushed a commit fixing an example I missed before and [doc build].

The CircleCI build is green and the build doc looks fine AFAICT (I compared the generated doc in this PR vs the dev doc visually, using https://53032-843222-gh.circle-artifacts.com/0/doc/_changed.html).

FYI the CircleCI is green on master too: https://circleci.com/gh/scikit-learn/scikit-learn/53038 (you never know the pdf build is more finicky sometimes ...).

Thanks for fixing this everyone