fix error:
```
Traceback (most recent call last):
File "engine.py", line 26, in <module>
import actions.strategy
File "/root/geneva/actions/strategy.py", line 4, in <module>
import actions.tree
File "/root/geneva/actions/tree.py", line 8, in <module>
import anytree
ImportError: No module named 'anytree'
```