Markdown issue: python syntax highlighting

[mhooreman]

Hello,

When I push the following in markdown, the syntax highlighting has an issue: string coloration is not correctly closed, so that there is a balancing between correct and incorrect lines.

When I export as HTML, the problem is not present.

```python
(
    (
        r'^(DP.*-)[\dX]*(.*)$',
        r'\1\2',
    ), (
        r'-$',
        '',
    )
)
```

Lines 3 to line 6 exluding the final comma are highlighted in red continuously, like a single string.

• notebook 5.7.0
• python 3.6.6
• happens both with chrome on windows and firefox on linux