py/objfloat: Fix case of raising 0 to -infinity.

It was raising an exception but it should return infinity.

py/objfloat.c

@@ -293,7 +293,7 @@ mp_obj_t mp_obj_float_binary_op(mp_binary_op_t op, mp_float_t lhs_val, mp_obj_t
             break;
         case MP_BINARY_OP_POWER:
         case MP_BINARY_OP_INPLACE_POWER:
-            if (lhs_val == 0 && rhs_val < 0) {
+            if (lhs_val == 0 && rhs_val < 0 && !isinf(rhs_val)) {
                 goto zero_division_error;
             }
             if (lhs_val < 0 && rhs_val != MICROPY_FLOAT_C_FUN(floor)(rhs_val)) {

tests/float/builtin_float_pow.py

@@ -0,0 +1,11 @@
+# test builtin pow function with float args
+
+print(pow(0.0, 0.0))
+print(pow(0, 1.0))
+print(pow(1.0, 1))
+print(pow(2.0, 3.0))
+print(pow(2.0, -4.0))
+
+print(pow(0.0, float('inf')))
+print(pow(0.0, float('-inf')))
+print(pow(0.0, float('nan')))