Limited lines to 119 characters in django/{contrib,db}.

Refs #23395.

https://code.djangoproject.com/ticket/23395
similar to the hanging indent for messages, for string interpolation I like:
```
return "Graph: %s nodes, %s edges" % (
    len(self.nodes),
    sum(len(x) for x in self.dependencies.values())),
)
```