Add functions PyUnicode_Append() and PyUnicode_AppendAndDel() that mirror
PyString_Concat() and PyString_ConcatAndDel() (the name PyUnicode_Concat()
was already taken).

Change PyObject_Repr() to always return a unicode object.

Update all repr implementations to return unicode objects.

Add a function PyObject_ReprStr8() that calls PyObject_Repr() and converts
the result to an 8bit string.

Use PyObject_ReprStr8() where using PyObject_Repr() can't be done
straightforward.
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index eb73f07..c3f198e 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -2084,7 +2084,7 @@
 static PyObject *
 count_repr(countobject *lz)
 {
-	return PyString_FromFormat("count(%zd)", lz->cnt);
+	return PyUnicode_FromFormat("count(%zd)", lz->cnt);
 }
 
 PyDoc_STRVAR(count_doc,
@@ -2396,11 +2396,11 @@
 		return NULL;
 
 	if (ro->cnt == -1)
-		result = PyString_FromFormat("repeat(%s)",
-			PyString_AS_STRING(objrepr));
+		result = PyUnicode_FromFormat("repeat(%U)",
+			objrepr);
 	else
-		result = PyString_FromFormat("repeat(%s, %zd)",
-			PyString_AS_STRING(objrepr), ro->cnt);
+		result = PyUnicode_FromFormat("repeat(%U, %zd)",
+			objrepr, ro->cnt);
 	Py_DECREF(objrepr);
 	return result;
 }