'Fails unless the given path (file or directory) exists.
The path can be given as an exact path or as a glob pattern.
The pattern matching syntax is explained in `introduction`.
The default error message can be overridden with the ``msg`` argument.'

def should_exist(self, path, msg=None):

    path = self._absnorm(path)
    if (not self._glob(path)):
        self._fail(msg, ("Path    '%s'    does    not    exist." % path))
    self._link("Path    '%s'    exists.", path)
