Documentation Error - pandas2ri causes ModuleNotFoundError
#### Code Sample, a copy-pastable example if possible

Compare
https://pandas.pydata.org/pandas-docs/version/0.23.3/r_interface.html
with
https://pandas.pydata.org/pandas-docs/version/0.23.4/r_interface.html


```python
from rpy2.robjects import pandas2ri
...
```
#### Problem description

The import generates a ModuleNotFoundError