Constant input warning in partial correlation reconstructor

[sdmccabe]

From the tests:

tests/test_reconstruction.py::test_graph_size
tests/test_reconstruction.py::test_partial_correlation
  /home/main/.pyenv/versions/miniconda3-latest/lib/python3.6/site-packages/scipy/stats/stats.py:3399: PearsonRConstantInputWarning: An input array is constant; the correlation coefficent is not defined.
    warnings.warn(PearsonRConstantInputWarning())

Don't recall seeing this before, maybe a new warning in scipy? Plausible that the warning is nothing, but should explore further.

[sdmccabe]

I didn't get this warning in an IPython session.

G = nx.ring_of_cliques(4, 16)
TS = netrd.dynamics.SherringtonKirkpatrickIsing().simulate(G, 1000)
H = netrd.reconstruction.PartialCorrelationMatrix().fit(TS)

[admercs]

This simply occurs when one of the input arrays contains constant values:

pearsonr([0,1,2,3], [0,0,0,0])