This reminds me of an option in os.walk:

"""
By default errors from the os.listdir() call are ignored. If optional
argument onerror is specified, it should be a function; it will be
called with one argument, an OSError instance. It can report the error
to continue with the walk, or raise the exception to abort the walk.
Note that the filename is available as the filename attribute of the
exception object.
"""

We could do something similar, except that by default, errors are not
ignored.