The checkstyle.py script depends on external tools. Those dependencies
are handled in different ways in different parts of the code. Centralize
the management of checker-specific dependencies to simplify the checkers
and output more consistent error messages.
This fixes a crash in the Pep8Formatter class when the autopep8
dependency is not found.
Fixes: 8ffaf376bb ("utils: checkstyle: Add a python formatter")
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
7ff6fd9774