Bug#956882: statsmodels: FTBFS on armel

[Rebecca N. Palmer]

Control: tags -1 patch

The failed tests are expecting an 0/0 warning from numpy, which it 
produces on amd64 but not armel:

amd64$ python3
Python 3.8.2 (default, Apr  1 2020, 15:52:55)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
 >>> import numpy as np;a=np.array([1.2,0.0,5.5])
 >>> a/a
<stdin>:1: RuntimeWarning: invalid value encountered in true_divide
array([ 1., nan,  1.])
 >>>
qemu-armel$ python3
Python 3.8.2 (default, Apr  1 2020, 15:39:53)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
 >>> import numpy as np;a=np.array([1.2,0.0,5.5])
 >>> a/a
array([ 1., nan,  1.])
 >>>

This implies that this is a test failure but not a user-level bug, so 
removing this warning check is an appropriate fix.