Prevent XRef issue when analysis runs on generated code

[kivra-pauoli]

Motivation

It is not guaranteed that a generated module contains a file attribute. I've seen erlydtl-generated modules that don't have it.

It's potentially possible to not see the error by making use of xref_queries (?) though I didn't test that thoroughly (I will have to eventually use it though, since some generated modules do appear to have the file attribute, but I'm still to understand where it's coming from).

On the other hand, instead of simply removing the analysis (as per the code comment) we could also output a special

module <module>: ...

with the error.

Review notes

Probably best seen with "Hide whitespace" enabled.

[kivra-pauoli]

For reference, the query to prevent analysis of e.g. exports_not_used over erlydtl-issued modules can be something like

{xref_queries, [
    {"X - XU - (\".*_dtl_.*\":\".*\"/\".*\")" % exports not used (except *_dtl_* modules)
    , []
    }
]}.

[ferd]

Seems pretty alright. Turns a crash into a returned error and the substitution of module_not_found is probably good enough to go on with this.

[ferd]

Thanks for the contribution, and sorry for the slow review!