It is a guard against a stack overflow, yes. Python (or rather, the CPython implementation) doesn’t optimize tail recursion, and unbridled recursion causes stack overflows. You can check the recursion limit with sys.getrecursionlimit:
import sys
print(sys.getrecursionlimit())
and change the recursion limit with sys.setrecursionlimit:
sys.setrecursionlimit(1500)
but doing so is dangerous — the standard limit is a little conservative, but Python stackframes can be quite big.
Python isn’t a functional language and tail recursion is not a particularly efficient technique. Rewriting the algorithm iteratively, if possible, is generally a better idea.