Some assemblies in the NCBI database does not have a fna/fasta files.

[waterflow80]

I have noticed that some assemblies, in the NCBI database, does not have a corresponding fna/fasta file alongside their assembly_report file. Like this one for example: GCF_000001405.10.
While others do: GCF_000001405.26.

So this can be confusing while retrieving the data, because this means that we cannot retrieve the information of a seqCol object of any corresponding assembly accession.
There will be some limitations.

[tcezard]

This is dues to some assembly predating standard that are in use today. I would suggest that we assume the assembly is present and if not that we would fail gracefully. However this is not of the highest priority.