Extend test coverage of the validate_file script #1754

Job	Run time
Lint	1m 21s
Test frontend	28s
Test mcp-server on 3.8	6m 21s
Test mcp-server on 3.9	6m 18s
Test mcp-server on 3.10	8m 37s
Test mcp-server on 3.11	8m 37s
Test mcp-server on 3.12	9m 41s
Test mcp-client on 3.8	9m 1s
Test mcp-client on 3.9	8m 32s
Test mcp-client on 3.10	9m 22s
Test mcp-client on 3.11	9m 35s
Test mcp-client on 3.12	9m 38s
Test dashboard on 3.8	9m 19s
Test dashboard on 3.9	9m 4s
Test dashboard on 3.10	9m 6s
Test dashboard on 3.11	9m 31s
Test dashboard on 3.12	11m 2s
Test archivematica-common on 3.8	8m 8s
Test archivematica-common on 3.9	8m 22s
Test archivematica-common on 3.10	9m 8s
Test archivematica-common on 3.11	9m 3s
Test archivematica-common on 3.12	10m 9s
Test storage-service on 3.9	6m 6s
Test migrations on 3.9	5m 38s
	3h 12m 7s

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