Django help_text line length convention

I was wondering what the convention was for line length when inputting help_text and other hard-coded long lines into Python/Django. I have read PEP-8, where line length is covered for code and comments, however I am not sure how this applies for long strings of text.

This is the for the field 'explanation_text', and the help_text field option.

class Question(models.Model):
    questionnaire = models.ForeignKey(Questionnaire, on_delete=models.CASCADE)
    title = models.CharField(max_length=150, blank=False)
    category = models.CharField(max_length=20, blank=False)
    created_date = models.DateTimeField(default=datetime.now, blank=True)
    explanation_text = models.TextField(
        blank=True,
        help_text="Explanation text goes here. Candidates will be able to see this after they have taken a questionnaire. To change this, refer to the setting on questionnaire administration. Max length is 1000 characters.",
        max_length=1000)

    def __str__(self):
        return self.title