objgenerator: Implement throwing exceptions out of generator.

py/objgenerator.c

@@ -103,8 +103,10 @@ STATIC mp_obj_t gen_next_send(mp_obj_t self_in, mp_obj_t send_value) {
             return *self->sp;
 
         case MP_VM_RETURN_EXCEPTION:
+            self->ip = 0;
+            nlr_jump(self->state[self->n_state - 1]);
+
         default:
-            // TODO
             assert(0);
             return mp_const_none;
     }

tests/basics/generator-exc.py

@@ -9,3 +9,23 @@ def gen():
 
 for i in gen():
     print(i)
+
+
+# Test throwing exceptions out of generator
+def gen2():
+    yield 1
+    raise ValueError
+    yield 2
+    yield 3
+
+g = gen2()
+print(next(g))
+try:
+    print(next(g))
+except ValueError:
+    print("ValueError")
+
+try:
+    print(next(g))
+except StopIteration:
+    print("StopIteration")