https://github.com/asottile/pyupgrade

> A tool to automatically upgrade syntax for newer versions of the
> language.

- Drop u str prefix
- Drop base object inheritance
- Drop args to super()
- Use set literals
- Use dict comprehension
- Use set comprehension

In Python 3, the default encoding of source files is utf-8. The encoding
cookie is now unnecessary and redundant so remove it. For more details,
see the docs:

https://docs.python.org/3/howto/unicode.html#the-string-type

> The default encoding for Python source code is UTF-8, so you can
> simply include a Unicode character in a string literal ...

Includes a fix for the flake8 header checks to stop expecting an
encoding cookie.

* Fixes #5426: [Napoleon] Better handling of inline attributes

* Removes uneeded NOQA comments

* Fixes imports

This lets napoleon render exceptions using the standard info field
syntax
```
:raises FooException: Some condition.
```
rather than the nonstandard
```
:raises: :exc:`FooException` -- Some condition.
```

Note that the previous approach was more forgiving if an explanatory
text was given in the Raises section without an actual exception class:
```
Raises
------
If something occurs.
```
would be rendered as
```
:raises: *If something occurs*
```
which is OK-ish but is now rendered as
```
:raises If something occurs.:
```
which is somewhat more nonsensical.

However neither the Google style guide nor numpydoc actually support
this form (they always have both the type and the description) so I
think the change is reasonable.