curds: Switch to using the asyncio module for testing threading

I'm planning to use the asyncio code for running background threads, so
let's switch to it for now to get a feel for how it works.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

curds/test_album.py

@@ -1,6 +1,7 @@
 # Copyright 2019 (c) Anna Schumaker
+import asyncio
+import concurrent.futures
 import hashlib
-from multiprocessing.pool import ThreadPool
 import unittest
 import album
 
@@ -58,8 +59,8 @@ class TestAlbumClass(unittest.TestCase):
 
     def test_parallel_lookup(self):
         album.album_map.clear()
-        with ThreadPool(processes=5) as pool:
-            res = pool.map(album.lookup, [ album_info ] * 20)
+        with concurrent.futures.ThreadPoolExecutor(max_workers=5) as pool:
+            res = list(pool.map(album.lookup, [ album_info ] * 20))
             self.assertIsNotNone(res[0])
             self.assertEqual(res.count(res[0]), 20)
         self.assertEqual(len(album.album_map), 1)