gitmodules references things that need permission to checkout
when the build system wants to checkout/make.tar.xz for this package, then it tries to check out submodules as well, but gitlab.labs.nic.cz is not configured to accept anonymous checkouts:
HEAD is now at 5d6e645 Change from atf-marvell to official arm-trusted-firmware
Submodule 'arm-trusted-firmware' (https://github.com/ARM-software/arm-trusted-firmware/) registered for path 'arm-trusted-firmware'
Submodule 'mox-imager' (git@gitlab.labs.nic.cz:turris/mox-imager.git) registered for path 'mox-imager'
Submodule 'u-boot' (git@gitlab.labs.nic.cz:turris/mox-u-boot.git) registered for path 'u-boot'
Cloning into '/mnt/caches/turris-build/build/tmp/dl/u-boot-mox-2018-11-rc1/arm-trusted-firmware'...
Cloning into '/mnt/caches/turris-build/build/tmp/dl/u-boot-mox-2018-11-rc1/mox-imager'...
git@gitlab.labs.nic.cz: Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
fatal: clone of 'git@gitlab.labs.nic.cz:turris/mox-imager.git' into submodule path '/mnt/caches/turris-build/build/tmp/dl/u-> boot-mox-2018-11-rc1/mox-imager' failed
Failed to clone 'mox-imager'. Retry scheduled
Cloning into '/mnt/caches/turris-build/build/tmp/dl/u-boot-mox-2018-11-rc1/u-boot'...
git@gitlab.labs.nic.cz: Permission denied (publickey).
fatal: Could not read from remote repository.