sed: expression #1, char 20: unknown command: `3'

[pitchum]

Describe the bug

VPN configuration fails with some .cube files.

Someone reported this: https://forum.yunohost.org/t/probleme-dinstallation-de-yunohost-sur-ma-brique/18650/6

Steps to reproduce

Having a cube file containing "openvpn_rm": [..., "route-ipv6 2000::/3", ...] and launch the following command:

yunohost app config set vpnclient --args config_file=/path/to/bad_config.cube

which ends like this:

Info: Transforming .cube into OVPN file
Warning: sed:  expression #1, char 20: unknown command: `3'