forecast.py exits with "done" even when a task failed #82
Description
When one of the parallel tasks in forecast.py fails, the ERROR message(s) are off the screen and all the user can see is
INFO - forecast.py done
The underlying reason is that execute() does not distinguish error exits. Adding return value to indicate an error and message
ERROR - At least one parallel task failed, check for ERROR in the log above
in the case when execute() failed.