Pipeline configuration error in snakefile workflow

[Sarah Gale]

After following the demo for pipeline configuation, I received the following message after attempting to execute the file.

"WorkflowError in line 13 of path/Snakefile: Config file is not valid JSON or YAML. In case of YAML, make sure to not mix whitespace and tab indentation. File "path/Snakefile", line 13, in <module>"

Has anyone else run into this issue?