Feature request: Handle I/O errors more gracefully and continue iterating volumes

[d2x]

In the event of an I/O error from a failing disk, the script crashes (v0.8beta2). This could be handled a little better with a try / catch and perhaps throwing a warning that a volume failed to be backed up rather than outright crashing.

Volume 'vm-d8-root': Traceback (most recent call last):
  File "/usr/local/bin/wyng", line 4667, in <module>
    monitor_send(storage, aset, selected_vols, monitor_only=False)
  File "/usr/local/bin/wyng", line 3467, in monitor_send
    send_volume(storage, vol, curtime, ses_tags, send_all=datavol in send_alls)
  File "/usr/local/bin/wyng", line 3158, in send_volume
    vf_seek(addr)    ; buf = vf_read(chunksize)
OSError: [Errno 5] Input/output error
None
None

This may be better to have as a flag to "continue on error" rather than the default. Anyone running this in an unattended manner would likely prefer it to crash to trigger manual review.

Overall, really liking the wyng backup script.

[tasket]

Thanks for the report! FWIW, Wyng does have a concept of trying all then reporting errors at the end; this is done mostly for errors that are Wyng-specific. However, as you point out, the catching of system errors is sparse and could be expanded so that more volumes can be processed in an error-bound session.