[Checkins] [zopefoundation/Zope] 3448e3: Add pyupgrade via pre-commit (#868)

[Jürgen Gmach]

  Branch: refs/heads/master
  Home:   https://github.com/zopefoundation/Zope
  Commit: 3448e30439780a6495807b88ba6c1098225400bc
      https://github.com/zopefoundation/Zope/commit/3448e30439780a6495807b88ba6c1098225400bc
  Author: Jürgen Gmach <juergen.gmach at googlemail.com>
  Date:   2020-07-17 (Fri, 17 Jul 2020)

  Changed paths:
    A .pre-commit-config.yaml
    M CHANGES.rst
    M src/Products/PageTemplates/Expressions.py
    M src/Products/PageTemplates/engine.py
    M src/Products/PageTemplates/tests/testC2ZContext.py
    M src/Products/PageTemplates/tests/testVariables.py
    M src/Products/PageTemplates/tests/testZopeAwareEngine.py
    M tox.ini
    M util.py

  Log Message:
  -----------
  Add pyupgrade via pre-commit (#868)

`pre-commit` is a linter runner, which does all the heavy lifting of finding
the correct files to lint, recursively.

Also, `pre-commit` both is able to pin package versions, and to autoupdate
all at once if desired.

You can run `pre-commit` via `tox -e pre-commit` or you can install it, so
it runs every time you do a `git commit`.

For the latter, you need to have `pre-commit` in your path and enter once
`pre-commit install` while being in the root of this repository.