Verify improvements:
Check existence of parents of changesets and manifests
Count errors
Use ui for display
Catch and count unpack exceptions
Print error count and exit with non-zero status on error
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1c590d34bf61e2ea12c71738e5a746cd74586157 0.4e
7eca4cfa8aad5fce9a04f7d8acadcd0452e2f34e 0.4d
b4d0c3786ad3e47beacf8412157326a32b6d25a4 0.4c