Treat compiler warnings as errors for CI

Author: Connor Rigby

.circleci/config.yml

@@ -12,10 +12,10 @@ jobs:
       - run: mix local.hex --force
       - run: mix local.rebar --force
       - run: mix deps.get
-      - run: mix deps.compile
+      - run: mix deps.compile --warnings-as-errors
       - run: mix compile
       - run:
-          command: mix compile
+          command: mix compile --warnings-as-errors
           environment:
             MIX_ENV: test
       - save_cache:

test/sqlite/sqlite_test.exs

@@ -1,6 +1,6 @@
 defmodule SqliteTest do
   use ExUnit.Case
-  alias Sqlite.{Query, Error, Result}
+  alias Sqlite.{Result}
 
   describe "open/close" do
     test "opens a database" do