Handle properly too long string during import

DataError at /data-source-contribution/done/
value too long for type character varying(64)
Request Method:	GET
Request URL:	http://viralhostrangedb.pasteur.cloud/data-source-contribution/done/
/code/viralhostrangedb/business_process.py in import_file

176 virus = virus_dict[explicit_virus]
Local Vars
Variable	Value
data_source	
<DataSource: to_delete (created on 2019-10-23 14:32:20 UTC)>