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>

* all: remove "u" string prefix

* util: remove unirange

Since Python 3.3, all builds are wide unicode compatible.

* unistring: remove support for narrow-unicode builds

which stopped being relevant with Python 3.3

* a filter for math symbols

This filer replaces math symbols from e.g. LaTeX and Isabelle with
corresponding unicode. It could be expanded to other math-heavy
languages.

* add "symbols" filter to basic tests

This fixes three test failures on Windows:
* Two due to incorrect handling of : (on Windows, multiple : can
  be part of a path.)
* One due to newline differences

* Remove Python 2 compatibility

* remove 2/3 shims in pygments.util
* update setup.py metadata

* Remove unneeded object inheritance.

* Remove unneeded future imports.