If you set the pipeline name to just a number with no other characters, it looks like the YAML parser will automatically parse this as an int. Then at line 5879 in cpac_pipeline.py (prep_workflow) you will get this error when you try to concatenate the pipeline name to a fork label:
pipeline_id = c.pipelineName + forkPointsDict[strat]
TypeError: unsupported operand type(s) for +: 'int' and 'str'
If you set the pipeline name to just a number with no other characters, it looks like the YAML parser will automatically parse this as an int. Then at line 5879 in cpac_pipeline.py (prep_workflow) you will get this error when you try to concatenate the pipeline name to a fork label: