[dwgsim] 0 reads error for low coverage and short genomes

[simonepignotti]

When simulating reads for very short genomes (in this case 220bp) and very low coverage (1) the resulting number of reads to simulate is 0, which is not accepted by dwgsim.

"dwgsim" -1 150 -2 150 -z 1 -y 0 -N 0 -e 0.02 -E 0.02 -r 0.001 -R 0.15 -X 0.3 -d 500 -s 50.0 "viral/GCF_000839085.1_ViralProj14152_genomic/001/reference.fa" "viral/GCF_000839085.1_ViralProj14152_genomic/001/dwgsim_files.pe.1" > /dev/null
Error: command line option -N was out of range

To replicate this issue: Genome https://www.ncbi.nlm.nih.gov/assembly/GCF_000839085.1/ Coverage 1

rnftools.mishmash.DwgSim(
        fasta='viral/GCF_000839085.1_ViralProj14152_genomic.fna',
        coverage=1,
        read_length_1=150,
        read_length_2=150,
)

[simonepignotti]

Duplicate #53