exceptions which differ in numpy and pytorch

[ev-br]

In some cases NumPy and PyTorch raise different exception classes: numpy raises a ValueError or TypeError, while pytorch defaults to RuntimeError.

For instance (this one is straight from the numpy test suite) subtracting booleans :

In [12]: a = np.ones((), dtype=np.bool_); a - a
Input In [12], in <cell line: 1>()
----> 1 a = np.ones((), dtype=np.bool_); a - a

TypeError: numpy boolean subtract, the `-` operator, is not supported, use the bitwise_xor, the `^` operator, or the logical_xor function instead.

The matching pytorch call raises a RuntmeError.

For the time being, I'm adding a raises((TypeError, RuntimeError)) in the test suite, with an intention to revisit this later, and either translate exceptions everywhere, or just document the difference.

[ev-br]

Let's fold this into #5 and close as a duplicate.