**Blender Version**
Broken:
```
>>> bpy.app.version, bpy.app.build_hash
(2, 80, 40), b'a77b63c56943'
```
a builder.blender.org build from 6 jan 2019,
**Short description of error**
A function appended to `app.handlers.undo_pre` is called, but `app.handlers.undo_post` is not.. it seems to call `undo_pre` instead a second time.
**Exact steps for others to reproduce the error**
1. execute this script to set both `undo_pre` and `undo_post` app.handlers
```python
import bpy
from bpy.app.handlers import persistent
@persistent
def handler_undo_pre(scene):
print('pre')
@persistent
def handler_undo_post(scene):
print('post')
if __name__ == '__main__':
bpy.app.handlers.undo_pre.append(handler_undo_pre)
bpy.app.handlers.undo_post.append(handler_undo_post)
# bpy.app.handlers.undo_pre.remove(handler_undo_pre)
# bpy.app.handlers.undo_post.remove(handler_undo_post)
```
2. then trigger an undo. (maybe add a node the nodetree and press ctrl+z)
3. see the console/terminal. it prints
```
pre
pre
```