`./xtool setup` failed with no explicit error message.

[ddwolf]

the command and output is as below, I am running it on an ubuntu 14.04 machine.

$ ./xtool setup
Setting up the build environment...

• git submodule init / update...
  Cloning into 'third_party/glm'...
  remote: Counting objects: 46915, done.
  remote: Compressing objects: 100% (7/7), done.
  remote: Total 46915 (delta 2), reused 4 (delta 1), pack-reused 46907
  Receiving objects: 100% (46915/46915), 62.37 MiB | 4.36 MiB/s, done.
  error: RPC failed; result=56, HTTP code = 200
  Resolving deltas: 100% (34376/34376), done.
  Clone of 'https://github.com/g-truc/glm.git' into submodule path 'third_party/glm' failed
  Traceback (most recent call last):
  File "./xtool", line 1821, in
  sys.exit(main())
  File "./xtool", line 126, in main
  return_code = command.execute(args, pass_args, os.getcwd())
  File "./xtool", line 662, in execute
  git_submodule_update()
  File "./xtool", line 474, in git_submodule_update
  '--recursive',
  File "./xtool", line 324, in shell_call
  subprocess.check_call(command, shell=False, stdout=stdout_file)
  File "/usr/lib/python2.7/subprocess.py", line 540, in check_call
  raise CalledProcessError(retcode, cmd)
  subprocess.CalledProcessError: Command '['git', 'submodule', 'update', '--init', '--recursive']' returned non-zero exit status 1