From the OP:

> This was reported at [1] and originally at [2]. The readline maintainer suggests [3] using:
> 
>     rl_variable_bind ("enable-meta-key", "off");
> 
> which was introduced in readline 6.1. Do you think it'd be safe to add the above line?

From 3.4.3 final:

>     @unittest.skipIf(readline._READLINE_VERSION < 0x0600
>                      and "libedit" not in readline.__doc__,
>                      "not supported in this library version")


The test currently fails on readline version 6.0.  The version to test on needs a bump to 0x0610.