Bug 1547730 - Fix b''.join(rand.choice(bytestring)..) to use bytes() constructor instead r=glandium

Differential Revision: https://phabricator.services.mozilla.com/D28107

--HG--
extra : moz-landing-system : lando

python/mozbuild/mozpack/test/test_files.py

@@ -163,9 +163,8 @@ class TestDest(TestWithTmpDir):
         self.assertEqual(dest.read(), 'qux')
 
 
-rand = b''.join(random.choice(
-    b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')
-                for i in six.moves.xrange(131597))
+rand = bytes(random.choice(b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')
+             for i in six.moves.xrange(131597))
 samples = [
     b'',
     b'test',