This recently turned up as a failure on our master branch (xref pydata/xarray#794):
https://travis-ci.org/pydata/xarray/jobs/115522509

We get the error TypeError: type object argument after * must be a sequence, not generator from this line in dask.array:

I'm not sure why the dask test suite didn't pick this up, since you do appear to run tests against Python 2.6. The source appears to be @jcrist's PR #1024.