Infinite recursion after too many errors

[embray]

The following code, adapted from the doctests, results in a segfault:

from gappy import gap
x = [0, 1, 2]
for _ in range(0, 5000):
    try:
        _ = gap.Sum(*x)
    except ValueError:
        pass

The segfault is caught and handled by cysignals, but from thereafter other GAP errors result in a segfault as well.

However, replacing gap.Sum(*x) with gap.eval('Sum(0, 1, 2)'), although still resulting in a GAPError, does not appear to lead to this condition. So I think the bug is probably local to GapFunction.__call__. Though it's weird that it breaks all error handling.

[embray]

Provided a fix for this in gap at gap-system/gap#4258 but I should see if there's a way I can work around it, maybe with wrappers for GAP_Enter/Leave.

[embray]

Figured out exactly why the infinite recursion is happening, as explained here: gap-system/gap#4258 (comment)