pyupgrade is a tool to automatically upgrade syntax for newer versions
of the Python language.

The project has been Python 3 only since
35544e2fc6eed0ce4a27ec7285aac71ff0ddc473, allowing for several cleanups:

- Remove unnecessary "-*- coding: utf-8 -*-" cookie. Python 3 reads all
  source files as utf-8 by default.

- Replace IOError/EnvironmentError with OSError. Python 3 unified these
  exceptions. The old names are aliases only.

- Use the Python 3 shorter super() syntax.

- Remove "utf8" argument form encode/decode. In Python 3, this value is
  the default.

- Remove "r" from open() calls. In Python 3, this value is the default.

- Remove u prefix from Unicode strings. In Python 3, all strings are
  Unicode.

- Replace io.open() with builtin open(). In Python 3, these functions
  are functionally equivalent.

Co-authored-by: Matthäus G. Chajdas <Anteru@users.noreply.github.com>

Rust macros seem to fit more into the "magic function" category than into the "builtin" one.

Rust macros end with a '!'. The word border (regex '\b') for such expressions is located before the '!' (e. g. "print\b!(...)"). The regex here used the suffix option, which added an r'\b' after each regex (e. g. r'print!\b'). Therefore, the supplied regular expressions didn't match the rust macros.

To fix this problem, the suffix is removed. As every macro ends with an '!' (which implicitely includes a word border before), it's not necessary anyway.

'drop', 'Some', 'None', 'Ok' and 'Err' are types, not macros.