I was trying to run CrossMap for a set of bam files using this script. But its showing error.

bam_list <- list.files(path = "home_hg19_Bam/", pattern = ".bam$", full.names=T)

for (i in 1:length(bam_list)){
system(paste0("CrossMap.py bam ./hg18ToHg19.over.chain.gz", bam_list[i], folder, "home/SCLC_hg19_Bam/" ,gsub(".bam", "", bam_list[i]), "_hg19.bam"))}