0.13.0: Test failure due to a unit problem

[olebole]

🐞 Problem

When running the tests during build time, I get the following error:

_____________________ [doctest] poliastro.core.util.cross ______________________
143     b : ndarray
144         3 Dimension vector.
145 
146     Examples
147     --------
148     >>> from poliastro.core.util import cross
149     >>> from astropy import units as u
150     >>> i = [1, 0, 0] * u.m
151     >>> j = [0, 1, 0] * u.m
152     >>> cross(i, j)
UNEXPECTED EXCEPTION: TypeError('only dimensionless scalar quantities can be converted to Python scalars')
Traceback (most recent call last):

  File "/usr/lib/python3/dist-packages/astropy/units/quantity.py", line 715, in to_value
    scale = self.unit._to(unit)

  File "/usr/lib/python3/dist-packages/astropy/units/core.py", line 953, in _to
    "'{0!r}' is not a scaled version of '{1!r}'".format(self, other))

astropy.units.core.UnitConversionError: 'Unit("m2")' is not a scaled version of 'Unit(dimensionless)'

and similarly

/build/poliastro-0.13.0/.pybuild/cpython3_3.7/build/poliastro/core/util.py:152: UnexpectedException
______________________ [doctest] poliastro.core.util.norm ______________________
103     vec: ndarray
104         Dimension 3 vector.
105 
106 
107     Examples
108     --------
109     >>> from poliastro.core.util import norm
110     >>> from astropy import units as u
111     >>> vec = [1, 1, 1] * u.m
112     >>> norm(vec)
Expected:
    1.7320508075688772
Got:
    <Quantity 1.73205081 m>

/build/poliastro-0.13.0/.pybuild/cpython3_3.7/build/poliastro/core/util.py:112: DocTestFailure

Any idea here? Astropy version is 3.2.1.

[astrojuanlu]

Interestingly, these are bugs in our doctests and we never noticed them, perhaps because we only run them with numba. The poliastro.core functions are not meant to be used with units.

[astrojuanlu]

Thanks @olebole!