* Add CDDL lexer (thanks to Fabian Neumann)

* Add CDDL to mappings

* Fix inline flag in CDDL regex

* Update AUTHORS

* Fix explosive backtracking

* Comment invalid CDDL syntax for automated tests

* Update following Georg Brandl's review

* Update tests for CDDL to new framework

* Pylint pass

* Update links to CDDL RFC

* Update copyright header

* Solve regexlint issues in CDDL parser

* Add link to CDDL in documentation

Imported from:
https://github.com/nikeee/pygments-lexer-graphviz

See:
https://github.com/pygments/pygments/issues/731

docs to point to both snippets and examplefiles.

Co-authored-by: Georg Brandl <georg@python.org>

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>

see #1660