Remove the extra dimension: {windows,linux}. In local testing, this
suffix has no practical effect on test runs as the OS is always either
Linux or Window. Adding this suffixes forces many extra test runs when
simply using the command "tox". This has been removed to avoid these
extra runs. This allowed removing the environment variable PLATFORM.
Both Windows and Linux still run in CI.

Use only the component "crypto" to install the extra cryptography
package. This simplifies adding Python versions in the future as
modifying this line is no longer required.

Merge suffixes to one line: py{36,37,38,39}-{crypto,nocrypto}. Again,
this simplifies adding Python versions in the future as one needs to
modify only one line.

Update Python 2 syntax and drop Python-2-only examples.

Fix all Python console prompts to the full ">>> " for correct
highlighting.

Use "pycon" instead of "python" for interactive Python console session.
The "python" lexer is for Python scripts and doesn't interpret the ">>>"
prompt.

Fix all Python console code blocks to more accurately display what the
user will see. For example, when assigning a value to a variable, it
isn't also echoed.

Fix typo ".. code::" → ".. code-block::".

Use "console" instead of "sh" for shell sessions. The "sh" lexer is for
shell scripts. For a complete list of lexers, see:
https://pygments.org/docs/lexers/

Use blacken-docs to run black on code blocks. This is now included as a
pre-commit hook.

* Run tests against Python 3.9 and add trove classifier

* Loosen pin on cryptography to allow 3.x

* Setup GH Actions

* Remove src path changes

* Add dev extras

* Update USING_COVERAGE

* last update

* Upgrade pytest

* Remove 2.7 things