Hi, it is not possible to download index-system.asc. Bug seems to be similar to this issue:
Reproduction:
$ lxc-create -n test -t download
Setting up the GPG keyring
Downloading the image index
ERROR: Failed to download http://repo.turris.cz/lxc//meta/1.0/index-system.asc
lxc-create: test: lxccontainer.c: create_run_template: 1621 Failed to create container from template
lxc-create: test: tools/lxc_create.c: main: 319 Failed to create container test