Wait for up to a second for existing database lock to clear

This lets users queue new builds and otherwise schedule work while an ongoing
run is proceeding (with lots of record-progress hits). Arguably we want to
prioritize user-initiated commands to take effect and cancel ongoing
record-progress operations (and other automated work), but that will need more
care.

Author: Mark-Simulacrum

src/db/mod.rs

@@ -19,6 +19,7 @@ struct ConnectionCustomizer;
 impl CustomizeConnection<Connection, ::rusqlite::Error> for ConnectionCustomizer {
     fn on_acquire(&self, conn: &mut Connection) -> Result<(), ::rusqlite::Error> {
         conn.execute("PRAGMA foreign_keys = ON;", [])?;
+        conn.execute("PRAGMA busy_timeout = 1000;", [])?;
         Ok(())
     }
 }