Variable printing in command line messes up ui

This happens consistently on my machine. To reproduce:

1. pip install tensorflow
2. pudb3 pudberror.py
3. set breakpoint on line 5
4. print x twice in command line

`pudberror.py`
```python
import tensorflow as tf

x = tf.compat.v1.placeholder(tf.float32, shape=(1024, 1024))

print(x)
```


Reproduce the problem with pudberror.py: install tensorflow, launch pudb3, stop at line 5, and print x twice in the command line. Trace the command-line display behavior after the second print and verify that repeated variable printing leaves the debugger UI intact.

Written by the indexing model from the issue text.