How can I avoid my import crashing with a Fatal Error due to an existing external ID?
Thanks to Jamie McClelland, there is a patch available to make this more user-friendly. At some point hopefully it will be merged into core.


JIRA: https://issues.civicrm.org/jira/browse/CRM-19664
PR: https://github.com/civicrm/civicrm-core/pull/9410


With this patch applied, instead of a fatal error, the import will continue and the problem rows will be pulled out in an error file at the end.