CP-37498: add flake8 config file
CP-37498: add flake8 config file

Eventually it would be good to replace the use of pylint in the
Makefile with flake8 but there are currently too many issues
needing to be resolved to permit this.

Signed-off-by: Mark Syms <655512b2a8f1aba6e4085462b623575da824f038@citrix.com>

xapi-project/sm,xapi-project/sm,xapi-project/sm