Bump py from 1.4.33 to 1.10.0

Bumps [py](https://github.com/pytest-dev/py) from 1.4.33 to 1.10.0.
- [Release notes](https://github.com/pytest-dev/py/releases)
- [Changelog](https://github.com/pytest-dev/py/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/py/compare/1.4.33...1.10.0

)

Signed-off-by: dependabot[bot] <support@github.com>

Give the correct length of remaining mapping items to expand in the variable view

Specifically this was coming out wrong with pandas DataFrames, for which
the length is the number of rows, but the keys are the columns.

Fix README screenshot situation

Improve the README file - Add new screenshot and recent screencast link

Run flake8 in Github CI on target Py version

Bump pygments dep for CVE-2021-27291

Make the type stringifier just call type(), convert old type stringifier to a "default" stringifier

Not needed anymore, I just forgot to remove this when I changed the
message to use the ui_log.

This message might also be more useful when reading in the settings
file- it can spam the user at this point if they've set an invalid
custom stringifier as their default stringifier in the config

This default is essentially what the old "type" stringifier was, but
with the addition that it also handles the logic for how to stringify
the "basic" types. This allows other stringifiers to be used on these
basic types now.

The "type" stringifier is now always just a way of viewing the type() of
a variable.

Pylint, actually drop Py2 compatibility

Fix reload_breakpoints functionality, to also (de)highlight lines in source window