Switch our python package management solution to poetry.

Mainly because it has better support for installing the packages from
different python versions.

It also has better dependency resolver than Pipenv. And supports modern
standard for python dependency management. This includes usage of
pyproject.toml for project specific configuration instead of per
tool conf files. See following links for details:
 https://pip.pypa.io/en/stable/reference/build-system/pyproject-toml/
 https://www.python.org/dev/peps/pep-0518/

scripts/pytest

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+# This is a helper script to run pytest without going too much
+# into python dependency management details
+
+# It may be desirable to create more sophisticated pytest launcher
+# with commonly used options to simplify launching from e.g CI
+
+poetry run pytest "${@:1}"