py3: fix test-hardlinks.t

Differential Revision: https://phab.mercurial-scm.org/D5096

contrib/python3-whitelist

@@ -214,6 +214,7 b' test-glog.t'
 test-gpg.t
 test-graft.t
 test-grep.t
+test-hardlinks.t
 test-hg-parseurl.py
 test-hghave.t
 test-hgignore.t

tests/test-hardlinks.t

@@ -19,8 +19,9 b" Some implementations of cp can't create "
   $ cat > linkcp.py <<EOF
   > from __future__ import absolute_import
   > import sys
-  > from mercurial import util
-  > util.copyfiles(sys.argv[1], sys.argv[2], hardlink=True)
+  > from mercurial import pycompat, util
+  > util.copyfiles(pycompat.fsencode(sys.argv[1]),
+  >                pycompat.fsencode(sys.argv[2]), hardlink=True)
   > EOF
 
   $ linkcp()