Some exceptions in importlib are raised from within except blocks, resulting in chained tracebacks. [1]  For at least some of these we should consider suppressing the exception context.

For example (for [1]):

        try:
            path = parent_module.__path__
        except AttributeError:
            msg = (_ERR_MSG + '; {} is not a package').format(name, parent)
            raise ImportError(msg, name=name) from None

[1] http://hg.python.org/cpython/file/default/Lib/importlib/_bootstrap.py#l2088