Python highlighting is broken for some triple quote docstrings #264

Prerequisites

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Description

Python highlighting is a bit broken with regard to triple quotes, see below.

Steps to Reproduce

1. Open a new file with Ctrl+N
2. Set to Python grammar using a button in bottom right.
3. Enter following text:

code:

class A:
    @classmethod
    def first(cls, iterable):
        """
        'REPLACE'
        """
        pass

    def other(self):
        pass

Expected behavior:

I expect the text between triple quotes (including them) to be colored as strings. Text that follows second triple quote should be highlighted as code.

Actual behavior:

All text following second triple quote till the end of file will be highlighted as a string.

Reproduces how often:

Everytime.

Versions

Atom : 1.28.1
Electron: 2.0.4
Chrome : 61.0.3163.100
Node : 8.9.3
OS: Ubuntu 18.04