pip21.3 has changed the behaviour of build - https://pip.pypa.io/en/stable/news/#v21-3 to use in-tree-build by default. this creates amalgamated files.
this will install as editable dependency during qa checks
for some reason mypy exclude for __amalgam__.py is not working
* flake8 fixes -- tests only
* fix ci failure
* integrate fix from is_3551 so tests will pass.
* Update tests/test_builtins.py
Co-authored-by: Gil Forsyth <gforsyth@users.noreply.github.com>