Remove unused import from embed_migrations!

[sgrif]

The changes for barrel support led to diesel_migrations exporting
everything required by this macro, leading to the warning being
generated.

Fixes #1739

[killercup]

Hm, this looks good at a first glance.

Thinking about it I'm not sure if this is not actually removing externally-visible imports. So while not important for diesel_migrations (because it hides the items in a mod), you might consider it a breaking change to migrations_macros. (This is very certainly not important in practice.)

[sgrif]

This isn't pub use

[killercup]

Oh but it's part of the derive macro's output and thus part of the user's code, right? But like I said, doesn't matter with the mod around it

[Eijebong]

@killercup Yeah, you can see it in the expanded code here #1739 (comment)

[0xcaff]

When will this fix be released?

[weiznich]

When will this fix be released?

See this comment for informations about the next release.

As workaround: Just add #![allow(unused_import)] to the module containing the macro call.