Fix assertion failure in mpz_divmod_inpl

.. turning this from an assertion failure into an exception:
    pow(1,1,0)

2 files changed, 9 insertions, 0 deletions

diff --git a/py/objint_mpz.c b/py/objint_mpz.c
index 7b5cb0b9d..808fae6e4 100644
--- a/py/objint_mpz.c
+++ b/py/objint_mpz.c
@@ -343,6 +343,10 @@ mp_obj_t mp_obj_int_pow3(mp_obj_t base, mp_obj_t exponent,  mp_obj_t modulus) {
         mpz_t *rhs = mp_mpz_for_int(exponent, &r_temp);
         mpz_t *mod = mp_mpz_for_int(modulus,  &m_temp);
 
+        if (mpz_is_zero(mod)) {
+            mp_raise_msg(&mp_type_ValueError, "pow() 3rd argument cannot be 0");
+        }
+
         mpz_pow3_inpl(&(res_p->mpz), lhs, rhs, mod);
 
         if (lhs == &l_temp) { mpz_deinit(lhs); }
diff --git a/tests/basics/builtin_pow3.py b/tests/basics/builtin_pow3.py
index 69b57e548..293a5acc9 100644
--- a/tests/basics/builtin_pow3.py
+++ b/tests/basics/builtin_pow3.py
@@ -22,3 +22,8 @@ try:
     print(pow(4, 5, "z"))
 except TypeError:
     print("TypeError expected")
+
+try:
+    print(pow(4, 5, 0))
+except ValueError:
+    print("ValueError expected")