What does `matrix_transpose` do when passed an array with fewer than 2 dimensions?

[brycelelbach]

The specification for `matrix_transpose does not specify what it does when you pass it a matrix with fewer than 2 dimensions. Do you get an error? Does it just return the array?

[shoyer]

I think it should be an error.

[rgommers]

We discussed this in the community meeting yesterday. There was agreement that this should be an error. @kgryte took the action to verify that this is already the case in all implementations, before closing this issue by making raising an exception required in the spec.