better error message than "Formatting error in sample sheet"

I think we can do better than giving this error:

cellranger/tenkit/mro/stages/make_fastqs/make_fastqs_preflight_local/__init__.py

Line 62 in e6517ca

martian.exit("Formatting error in sample sheet: %s" % csv_path)

I got this error for a _rna_bcl.csv file when I ran cellranger, and it didn't help to find the underlying problem.

So, I manually ran tk_sheet.file_is_simple_samplesheet(csv_path) on my file. Here's what I got:

WARNING:root:Unrecognized sample index: SI-TT-I9
WARNING:root:Unrecognized sample index: SI-TT-I10
WARNING:root:Unrecognized sample index: SI-TN-D8
WARNING:root:Unrecognized sample index: SI-TN-D9

This is helpful! We can check and see that SI-TT-I9 is not a valid sample index.

Now, I hope my cellranger run will finish without error if I fix this sample index.

It'd be ideal if the original error message would include this information.

Much appreciated Kamil - I was getting this error and your post helped me realize that it appears the sequencing center gave me the wrong indexes....