The error very generally just means something is broken, most likely in the code that you are porting to the sandbox location.
Some things to try:
- Check that matrix.cgi is not broken:
(you want to see a HTML block)
- Check that you are in fact copying the files that you think you are copying. If your CUSTOMIZATIONROOT is set to something, the install script may pick up files from there and not from where you are running the install.
Generally, you can use the -C flag with matrix.py commands to specify the customization root. To use the local one, do:
python matrix.py install your-location -C gmcs/