I am running yt-2.1stable with python2.7 on Kraken and run into this problem:

When I call a derived quantity that calls a derived field that calls a universal field, I get an error: "AttributeError: 'fake_parameter_file' object has no attribute 'parameters'" which arises in the universal field's convert function in 'data_objects/universal_fields.py'

With the following code:
#derived Field
def _test2(field,data):
        return data['Baryon_Overdensity']

add_field('test2',function=_test2,units=r"")

#derived quantity
def _test(data):
        return data['test2']

def _combTest(data,arr):
        return arr.sum()

add_quantity('test',function=_test,combine_function=_combTest,n_ret=1)

dd.quantities['test']()

I get the error:

AttributeError: 'fake_parameter_file' object has no attribute 'parameters'

from line 418, in _Convert_Baryon_Overdensity in universal_fields.py: "data.pf.parameters.has_key('omega_baryon_now'):"

So it seems as if the parameter file is not being passed from the derived quantitty all the way to the universal field. This works fine when I run it in serial, but fails when it is ran in parallel.
Any suggestions?

Thanks