[MASSEMBLY-779] It would be useful to be able to make the assembly plugin fail on errors

**[Benson Margulies](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=bmargulies)** opened **[MASSEMBLY-779](https://issues.apache.org/jira/browse/MASSEMBLY-779?redirect=false)** and commented

We've encountered some situations in which we would like our builds to fail if the assembly plugin cannot find some item called for in the descriptor.

This suggests the invention of a failOnMissingItem boolean parameter.

Default, of course, to current behavior.

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**Issue Links:**
- [MASSEMBLY-505](https://issues.apache.org/jira/browse/MASSEMBLY-505) Feature Request: useStrictFiltering option for FileSets
(_**"is blocked by"**_)

Start by reviewing how the assembly plugin processes descriptors and handles missing items, then read the linked MASSEMBLY-505 feature request about strict filtering. Done means adding a failOnMissingItem option that preserves current behavior by default and allows builds to fail when requested items cannot be found.

Written by the indexing model from the issue text.