code: def setup_container(builddir, _container):
      
      build_dir = local.path(builddir)
      in_dir = build_dir / "container-in"
      container_path = local.path(_container)
      with local.cwd(builddir):
          container_bin = container_path.basename
          container_in = in_dir / container_bin
          download.Copy(_container, container_in)
          uchrt = uchroot.no_args()
  
          with local.cwd("container-in"):
              uchrt = uchrt["-E", "-A", "-u", "0", "-g", "0", "-C", "-r", "/",
                            "-w",
                            os.path.abspath("."), "--"]
  
          # Check, if we need erlent support for this archive.
          has_erlent = bash[
              "-c", "tar --list -f './{0}' | grep --silent '.erlent'".format(
                  container_in)]
          has_erlent = (has_erlent & TF)
  
          # Unpack input container to: container-in
          if not has_erlent:
              cmd = local["/bin/tar"]["xf"]
              cmd = uchrt[cmd[container_bin]]
          else:
              cmd = tar["xf"]
              cmd = cmd[container_in]
  
          with local.cwd("container-in"):
              cmd("--exclude=dev/*")
          rm(container_in)
      return in_dir
docs: Prepare the container and returns the path where it can be found.