This breaks with a Singular Matrix problem in the Hessian calculation.
It took me two hours of figuring out the singular matrix issue, before I thought of checking endog
I think we should add a basic check for this.
I haven't looked at the details yet.
related: I was looking at using Logit for continuous variables in [0,1] interval, and it seemed to work.
We should raise an error if there are no zero values (endog==0).sum() == 0.
(endog==0).sum() == 0
ENH: Check binary input for correctness. Closes #1053.