* Use pytest-sphinx to have pytest run doctests in Sphinx docs rather
  than using Sphinx to run these via run_tests.py.

  * Sphinx is no longer a test dependency, which allows upgrading to
    Sphinx 6.0 while still being able to run the tests with Python 3.7.
    (Sphinx 6.0 dropped support for 3.7.)

  * Use conftest.py rather than testsetup or doctest_global_setup, which
    pytest-sphinx does not currently support.

  * Don't use :skipif: in doctest:: directives since pytest-sphinx does
    not currently support it (twmr/pytest-sphinx#9). Instead just
    don't ever run the one doctest that was using this, since the
    behavior it was testing is also covered by several tests in
    test_properties.py that do still properly get run conditionally
    (specifically, the "freed on zero refcount" tests are still run on
    CPython but not PyPy).

  * Don't use >>> for code we don't want to test, since pytest-sphinx
    will otherwise still run it even if it's in a code-block directive
    (and sprinkling `# doctest: SKIP` everywhere as an alternative is
    noisy).

* Add pytest-clarity to dev dependencies and pass -vv to pytest by
  default to enable pytest-clarity's nicer diffs in development.

* Use pytest-sphinx to have pytest run doctests in Sphinx docs rather
  than using Sphinx to run these via run_tests.py.

  * Sphinx is no longer a test dependency, which allows upgrading to
    Sphinx 6.0 while still being able to run the tests with Python 3.7.
    (Sphinx 6.0 dropped support for 3.7.)

  * Use conftest.py rather than testsetup or doctest_global_setup, which
    pytest-sphinx does not currently support.

  * Don't use :skipif: in doctest:: directives since pytest-sphinx does
    not currently support it (twmr/pytest-sphinx#9). Instead just
    don't ever run the one doctest that was using this, since the
    behavior it was testing is also covered by several tests in
    test_properties.py that do still properly get run conditionally
    (specifically, the "freed on zero refcount" tests are still run on
    CPython but not PyPy).

  * Don't use >>> for code we don't want to test, since pytest-sphinx
    will otherwise still run it even if it's in a code-block directive
    (and sprinkling `# doctest: SKIP` everywhere as an alternative is
    noisy).

* Add pytest-clarity to dev dependencies and pass -vv to pytest by
  default to enable pytest-clarity's nicer diffs in development.

* Use pytest-sphinx to have pytest run doctests in Sphinx docs rather
  than using Sphinx to run these via run_tests.py.

  * Sphinx is no longer a test dependency, which allows upgrading to
    Sphinx 6.0 while still being able to run the tests with Python 3.7.
    (Sphinx 6.0 dropped support for 3.7.)

  * Use conftest.py rather than testsetup or doctest_global_setup, which
    pytest-sphinx does not currently support.

  * Don't use :skipif: in doctest:: directives since pytest-sphinx does
    not currently support it (twmr/pytest-sphinx#9). Instead just
    don't ever run the one doctest that was using this, since the
    behavior it was testing is also covered by several tests in
    test_properties.py that do still properly get run conditionally
    (specifically, the "freed on zero refcount" tests are still run on
    CPython but not PyPy).

  * Don't use >>> for code we don't want to test, since pytest-sphinx
    will otherwise still run it even if it's in a code-block directive
    (and sprinkling `# doctest: SKIP` everywhere as an alternative is
    noisy).

* Add pytest-clarity to dev dependencies and pass -vv to pytest by
  default to enable pytest-clarity's nicer diffs in development.