YAML generation failure report needs improvement

[ljwh2]

Metadata Yaml generation occasionally fails. A daily Metadata YAML generation report is generated and delivered to gwas-dev, in order that sumstats with missing yaml files can be promptly fixed.

Several times curators have spotted missing yaml files that did not appear in the report e.g https://github.com/EBISPOT/goci/issues/1720 Conversely, when eported failures are investigated, it seems they are often not true failures but triggered when there is a delay between releasing the file to ftp and generating the yaml due to backlog.

This needs investigating and improving in order that the failure report fulfils it's aims.