Use only py::error_already_set as that's the least heavy of them. Also
changed all occurences of "throw" to "raise" so next time I'm doing a
prune of all C++ exceptions for good, those are easy to find.
That makes it much easier to handle in that case (because that's the
whole point of static builds) and also nicely circumvents any issues
with duplicated global data when a static lib would be linked to
multiple dynamic libraries.
Vladimír Vondruš