Improve error message when DSS fails to start up due to disk being full

Turribeach

If any idea can be quick win, this is the one! Recently we faced an issue whereby DSS failed to start with the following error:

Error: Cannot open an HTTP server: socket.error reported errno.ENOSPC (28)
For help, use /dataiku/dataiku-dss-11.2.1/python.packages/supervisor/supervisord.py -h

Running the suggested command produced even more confusing error:

Traceback (most recent call last):
  File "/dataiku/dataiku-dss-11.2.1/python.packages/supervisor/supervisord.py", line 37, in <module>
    from supervisor.medusa import asyncore_25 as asyncore
ImportError: No module named supervisor.medusa

Turns out these errors are all to do with the DSS DATA_DIR disk running out of space! So obviously the ask here is to make this error more user friendly. Having said that the easiest way will be to add a few lines of code to the dss startup script to check for available space before starting and fail to start with a meaningful message if the disk is full.

Homework for Dataiku Dev prioritising this enhancement: work out how many support tickets has this misleading error generated. At least 2 of those are ours...