Script looks for "DE1_0_2008_to_2010_Carrier_Claims_Sample_4.csv" file. ( not for DE1_0_2008_to_2010_Carrier_Claims_Sample_4A.csv or DE1_0_2008_to_2010_Carrier_Claims_Sample_4B.csv) and didn't found it.
Please download the latest master branch. There was some irregularities with file naming at the CMS web site which we fixed in our code that downloads, sorts and merges files.
I run script from unm-improvements branch and found error
Script looks for "DE1_0_2008_to_2010_Carrier_Claims_Sample_4.csv" file. ( not for DE1_0_2008_to_2010_Carrier_Claims_Sample_4A.csv or DE1_0_2008_to_2010_Carrier_Claims_Sample_4B.csv) and didn't found it.
I think it here