I'm getting a weird failure in the annotate particles callback that I'm having trouble reproducing on another machine. 

Here is the error message output I'm getting: http://paste.yt-project.org/show/7048/   . I'm just doing a simple:

$ sp = yt.SlicePlot(ds, 'z', 'density')

$ sp.annotate_particles(0.9)

$ sp.save()

This error occurs only on a machine where I have yt installed from source (version 3.3.4, changeset 6e21d8723012 of the stable branch.. this also occured on changeset 7f76a9ccfcca). I could not reproduce the error on a local machine where I've installed yt using anaconda (yt version 3.3.4). It fails on a ProjectionPlot as well.

Any thoughts on what could be causing this?

Thanks,

Andrew

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