Don't swallow error on startup (rebased onto develop)



This is the same as gh-2689 but rebased onto develop.

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Startup errors which could point to the actual failure
were being swallowed by Blitz. NB: This particular error
condition was initially related to the Ice.IPv6 setting.

See:
* https://www.openmicroscopy.org/community/viewtopic.php?f=5&t=7527
* https://www.openmicroscopy.org/community/viewtopic.php?f=5&t=7456&p=14166#p14166