add_operators(): the __floordiv__ and __truediv__ descriptors (and
their 'i' and 'r' variants) were not being generated if the
corresponding nb_ slots were present in the type object.  I bet this
is because floor and true division were introduced after I last
looked at that part of the code.
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 1354b81..0e6099c 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1837,6 +1837,8 @@
 BINARY(and, "x&y");
 BINARY(xor, "x^y");
 BINARY(or, "x|y");
+BINARY(floordiv, "x//y");
+BINARY(truediv, "x/y # true division");
 
 static PyObject *
 wrap_ternaryfunc(PyObject *self, PyObject *args, void *wrapped)
@@ -1915,6 +1917,8 @@
 IBINARY(iand, "x&=y");
 IBINARY(ixor, "x^=y");
 IBINARY(ior, "x|=y");
+IBINARY(ifloordiv, "x//=y");
+IBINARY(itruediv, "x/=y # true division");
 
 #undef ITERNARY
 #define ITERNARY(NAME, OP) \
@@ -2586,6 +2590,12 @@
 		ADD(nb->nb_inplace_and, tab_iand);
 		ADD(nb->nb_inplace_xor, tab_ixor);
 		ADD(nb->nb_inplace_or, tab_ior);
+		if (type->tp_flags & Py_TPFLAGS_CHECKTYPES) {
+			ADD(nb->nb_floor_divide, tab_floordiv);
+			ADD(nb->nb_true_divide, tab_truediv);
+			ADD(nb->nb_inplace_floor_divide, tab_ifloordiv);
+			ADD(nb->nb_inplace_true_divide, tab_itruediv);
+		}
 	}
 
 	ADD(type->tp_getattro, tab_getattr);