def on_cleanup_error(function, path, excinfo):
                click.secho("warning: failed to remove file or directory: {}\n"
                            "please delete it manually.".format(path),
                            fg="red")
def dec_c(self, ind):
        r, c = self.row_col(ind)
        c -= 1
        if c < 0:
            c = self.nc - 1
        if r == (self.nr - 1) and c == (self.nc - 1):
            c = self.nc - 2
        return self.indx(r, c)