refactor(paroxysm): Explicitly macro imports, no more 'extern crate'

Removes all but one occurence of `extern crate`, to conform with Rust
2018.

The last one is necessary because Diesel is a giant jungle of
complicated macros re-exported from private crates, and the current
version makes it hard to import those directly instead.

Change-Id: Id14165a456d5c3ce6f7a4e0222c611640113eb11
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1549
Tested-by: BuildkiteCI
Reviewed-by: kanepyork <rikingcoding@gmail.com>

fun/paroxysm/src/keyword.rs

@@ -2,6 +2,7 @@ use crate::models::{Entry, Keyword, NewEntry, NewKeyword};
 use diesel::pg::PgConnection;
 use diesel::prelude::*;
 use failure::Error;
+use failure::format_err;
 use std::borrow::Cow;
 
 /// Maximum number of times we'll follow a `see: ` pointer.