* y/loadAt.9:
  - vb [ci skip]
  - force recognizing ellipsis
  - try to fix changed traceback representation
  - select more specific pypy versions
  - prepare release 5.7.0
  - revert 5b8e2dc1

* master:
  - vb [ci skip]
  - force recognizing ellipsis
  - try to fix changed traceback representation
  - select more specific pypy versions
  - prepare release 5.7.0
  - revert 5b8e2dc1

Make flake8 happy

src/ZODB/DemoStorage.py:388:80: E501 line too long (89 > 79 characters)
src/ZODB/DemoStorage.py:391:80: E501 line too long (87 > 79 characters)
src/ZODB/DemoStorage.py:393:80: E501 line too long (83 > 79 characters)
src/ZODB/DemoStorage.py:395:80: E501 line too long (87 > 79 characters)
src/ZODB/DemoStorage.py:397:80: E501 line too long (100 > 79 characters)
src/ZODB/DemoStorage.py:398:80: E501 line too long (86 > 79 characters)
src/ZODB/DemoStorage.py:408:5: E303 too many blank lines (2)
src/ZODB/tests/testDemoStorage.py:397:9: F401 'ZODB.FileStorage.FileStorage' imported but unused
src/ZODB/tests/testDemoStorage.py:399:80: E501 line too long (101 > 79 characters)

loadAt -> loadBeforeEx since it was renamed so on
https://github.com/zopefoundation/ZODB/pull/323/commits/805bf36f .

* y/loadAt.8: (35 commits)
  Make lint happy
  Let the year float.
  Configuring for pure-python
  Specify a PyPy2 version.
  Lint the code.
  Configuring for pure-python
  Fix TypeError for fsoids (#351)
  Fix deprecation warnings occurring on Python 3.10.
  fix more PY3 incompatibilities in `fsstats`
  fix Python 3 incompatibility for `fsstats`
  add `fsdump/fsstats` test
  fsdump/fsstats improvements
  Undeprecate loadBefore
  fixup! changes: Add draft entry for loadAt/loadBeforeEx/DemoStorage fix
  changes: Add draft entry for loadAt/loadBeforeEx/DemoStorage fix
  fixup! Handle NotImplementedError raised by loadBefore/loadBeforeEx as "interface not provided"
  *: Don't emit warnings on loadBefore
  Handle NotImplementedError raised by loadBefore/loadBeforeEx as "interface not provided"
  loadAt -> loadBeforeEx
  - add coverage combine step
  ...

Sorry, but some of flake8 complaints are really stupid...

Resolve many conflicts after https://github.com/zopefoundation/ZODB/pull/357.

* master:
  Let the year float.
  Configuring for pure-python
  Specify a PyPy2 version.
  Lint the code.
  Configuring for pure-python

* Config with pure python
* Lint the code.
* Add support for Python 3.9 and 3.10.

to resolve trivial conflict on CHANGES.rst

* origin/master: (22 commits)
  Fix TypeError for fsoids (#351)
  Fix deprecation warnings occurring on Python 3.10.
  fix more PY3 incompatibilities in `fsstats`
  fix Python 3 incompatibility for `fsstats`
  add `fsdump/fsstats` test
  fsdump/fsstats improvements
  - add coverage combine step
  - first cut moving tests from Travis CI to GitHub Actions
  - ignore virtualenv artifacts [ci skip]
  tests: Run race-related tests with high frequency of switches between threads
  tests: Add test for load vs external invalidation race
  tests: Add test for open vs invalidation race
  fixup! doc/requirements: Require pygments < 2.6 on py2
  doc/requirements: Require pygments < 2.6 on py2
  fixup! buildout: Fix Sphinx install on Python2
  buildout: Fix Sphinx install on Python2
  Update README.rst
  Security fix documentation dependencies (#342)
  changes: Correct link to UnboundLocalError fsoids.py fix
  fsrefs: Optimize IO  (take 2) (#340)
  ...

Add support for Python 3.9 and 3.10.

Fix `TypeError: can't concat str to bytes` when running fsoids.py script with Python 3.

Closes #350

fsdump/fsstats improvements

Dieter Maurer notes that loadBefore cannot be deprecated yet because ZEO
essentially depends on the `end_tid` information returned by loadBefore
to update its cache:

https://github.com/zopefoundation/ZODB/pull/323#issuecomment-842021970

And to remove this dependency it would require to rework ZODB caching layer:

https://github.com/zopefoundation/ZODB/pull/323#issuecomment-845917355

So we cannot deprecate loadBefore until this rework is implemented first.

-> Remove general loadBefore deprecation, and emit loadBefore vs
loadBeforeEx warning only when actually hitting a "deletion" record,
because only that case is known to lead to data corruption.

@d-maurer says (https://github.com/zopefoundation/ZODB/pull/323#discussion_r627929959):

The changes around `loadBeforeEx` have much more impact than the `DemoStorage` fix.

--------

kirr: adjusted the text a bit: "Introduces" -> "Introduce"; add
"interface". @d-maurer, I hope it is ok.

The changelog entry uses loadBeforeEx, but we are likely to change this
name during https://github.com/zopefoundation/ZODB/pull/323 review.

loadBeforeEx uses the same docstring as loadBefore as @d-maurer suggests:

https://github.com/zopefoundation/ZODB/pull/323#discussion_r626255153

@d-maurer suggests to keep loadBefore without deprecation
(https://github.com/zopefoundation/ZODB/pull/323#pullrequestreview-650963363).

-> Don't emit warnings about deprecating loadBefore.

-> Keep the deprecation text in loadBefore interface, since loadBeforeEx
   should practically provide wider functionality without putting
   unnecessary constraint on storage implementations. In other words
   loadBefore deprecation is still there, but less aggressively
   advertised with the idea to make transition for outside-of-ZODB code
   to loadBeforeEx more smooth and with a bit more steps (we might want
   to reinstate the deprecation warnings at a later time).

Suggested by @d-maurer: https://github.com/zopefoundation/ZODB/pull/323#discussion_r625573381

@d-maurer suggests[1]:

    The ZODB logic relating to historical data (including MVCC) was largely
    centered around before. You have changed this to at - requiring wide spread
    modifications. I would much prefer to keep the before centered approach...

    (https://github.com/zopefoundation/ZODB/pull/323#pullrequestreview-650963363)

So let's change "at"-based logic to "before"-based logic and rename the new
method from loadAt to loadBeforeEx.

Define the official expansion of "ZODB"

Switch from Travis CI to GitHub Actions for testing

As suggested by @d-maurer:

https://github.com/zopefoundation/ZODB/pull/345#issuecomment-822188305
https://github.com/zopefoundation/ZEO/issues/168#issuecomment-821829116

/reviewed-on https://github.com/zopefoundation/ZODB/pull/345