zodbconvert skips blobs silently

[jensens]

using as source a filesystem+blobstorage where blobstorage is not allowed access due to missing permissions, blobs are silently ignored. I'd expect here at least a warning.

[saily]

+1,

Thanks god i did not stumble over that issue...

[jamadden]

If I understand correctly (the source is a FileStorage, and the user running zodbconvert doesn't have operating system permissions to access the blob-dir, so existing blob data is silently skipped), then that's an issue to raise on the zopefoundation/ZODB tracker: zodbconvert is essentially storage agnostic, it doesn't really know anything special about other storages or how they are laid out or what warnings they should/shouldn't raise.

[jamadden]

AFAICS, the FileStorage code should raise an error on initialization if the blob-dir exists but isn't accessible. Please feel free to open a ZODB issue and link it back here if that's not the case. Please feel free to re-open if I misunderstand the problem.

It may be possible to neglect to specify the blob-dir in the zodbconvert configuration and that can lead to a similar issue in some cases (see #24).