Invalid Syntax

This probably is going to be a user issue rather than a code issue. I'm rather new with the Librem 5 and got stuck right at the start. I run a Debian Buster and have installed the required software. (docker from docker.com repo's) (I've symlinked /usr/bin/python to python3)

I'm getting a Syntax error when I run ./build.sh.

Step 15/15 : ENTRYPOINT chroot --userspec=$(cat /root/username):$(cat /root/username) / /data/anbox-build.sh
 ---> Using cache
 ---> f514f21a9e26
Successfully built f514f21a9e26
Successfully tagged anbox-build-trusty:latest
repo: warning: Python 2 is no longer supported; Please upgrade to Python 3.6+.
Downloading Repo source from https://gerrit.googlesource.com/git-repo
remote: Counting objects: 1, done
remote: Finding sources: 100% (30/30)
remote: Total 30 (delta 9), reused 30 (delta 9)
Unpacking objects: 100% (30/30), done.
repo: Updating release signing keys to keyset ver 2.3
Traceback (most recent call last):
  File "/src/.repo/repo/main.py", line 56, in <module>
    from subcmds.version import Version
  File "/src/.repo/repo/subcmds/__init__.py", line 38, in <module>
    ['%s' % name])
  File "/src/.repo/repo/subcmds/upload.py", line 27, in <module>
    from hooks import RepoHook
  File "/src/.repo/repo/hooks.py", line 472
    file=sys.stderr)
        ^
SyntaxError: invalid syntax

I hope you can make something of it but let me know if you need more information or if I can try something else.

Thanks in advance!