eng_python() seems to ignore a single line of code that does not generate output

[yihui]

Minimal reprex:

```{r}
knitr::knit_engines$set(python = reticulate::eng_python)
```

```{python}
x = "hi there"
print(x)
```

```{python}
y = x.split(" ")  # no output
```

```{python}
print(y)
```

Output (note that the second python code chunk is missing):

[jjallaire]

@kevinushey Let's see if we can get a fix in for this one (realize you aren't focused on the python engine right now but I think this might be a deal-breaker for knitr making reticulate the default)

[jjallaire]

I had to do a patch release of reticulate for another reason and as a result this fix is now on CRAN in v1.3.1: https://cran.r-project.org/web/packages/reticulate/index.html

[yihui]

Excellent! I'll prepare a CRAN release of knitr soon.