py3: make tests/test-diff-antipatience.t work with python 3

On python3, if we do list(b'abcd'), we get [97, 98, 99, 100]. So this patch does
the list() operation on unicodes and then convert things to bytes.

This also adds `and None` to suppress return values of .write() calls.

Differential Revision: https://phab.mercurial-scm.org/D3833

contrib/python3-whitelist

@@ -88,6 +88,7 b' test-debugextensions.t'
 test-debugindexdot.t
 test-debugrename.t
 test-default-push.t
+test-diff-antipatience.t
 test-diff-binary-file.t
 test-diff-change.t
 test-diff-copy-depth.t

tests/test-diff-antipatience.t

@@ -11,9 +11,9 b''
 Test case that makes use of the weakness of patience diff algorithm
 
   $ hg init
-  >>> open('a', 'wb').write(b'\n'.join(list(b'a' + b'x' * 10 + b'u' + b'x' * 30 + b'a\n')))
+  >>> open('a', 'wb').write(('\n'.join(list('a' + 'x' * 10 + 'u' + 'x' * 30 + 'a\n'))).encode('ascii')) and None
   $ hg commit -m 1 -A a
-  >>> open('a', 'wb').write(b'\n'.join(list(b'b' + b'x' * 30 + b'u' + b'x' * 10 + b'b\n')))
+  >>> open('a', 'wb').write(('\n'.join(list('b' + 'x' * 30 + 'u' + 'x' * 10 + 'b\n'))).encode('ascii')) and None
 #if xdiff
   $ hg diff
   diff -r f0aeecb49805 a