[Toybox] [PATCH] ifconfig.test: don't check for specific error message.

[enh]

specifically, it was this kernel change, which seems reasonably motivated:

commit db0b99f59ae4d934a0af1a5670706d7c2a4b58ea
Author: Sabrina Dubroca <sd at queasysnail.net>
Date:   Fri Aug 23 15:44:36 2019 +0200

    ipv6: propagate ipv6_add_dev's error returns out of ipv6_find_idev

    Currently, ipv6_find_idev returns NULL when ipv6_add_dev fails,
    ignoring the specific error value. This results in addrconf_add_dev
    returning ENOBUFS in all cases, which is unfortunate in cases such as:

        # ip link add dummyX type dummy
        # ip link set dummyX mtu 1200 up
        # ip addr add 2000::/64 dev dummyX
        RTNETLINK answers: No buffer space available

    Commit a317a2f19da7 ("ipv6: fail early when creating netdev named all
    or default") introduced error returns in ipv6_add_dev. Before that,
    that function would simply return NULL for all failures.

    Signed-off-by: Sabrina Dubroca <sd at queasysnail.net>
    Signed-off-by: David S. Miller <davem at davemloft.net>

On Wed, Jan 22, 2020 at 8:08 AM enh <enh at google.com> wrote:
>
> A 5.4 kernel returns EINVAL rather than ENOBUFS when you try to
> configure an IPv6 address with the MTU set too small to support IPv6.
>
> Rather than check for both errors, just check for generic failure for
> now.
> ---
>  tests/ifconfig.test | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)