run-tests: python3.5 now supports mkdtemp using bytes for paths

Now that http://bugs.python.org/issue24230 is fixed (thanks to Gregory
Smith for that quick response!) we can drop one more ugly hack around
path handling. Tests still pass in 3.5 with this cleaner version, as
well as in 2.6.

tests/run-tests.py

@@ -1747,9 +1747,7 class TestRunner(object):
                 # without this, we get the default temp dir location, but
                 # in all lowercase, which causes troubles with paths (issue3490)
                 d = osenvironb.get(b'TMP', None)
-            # FILE BUG: mkdtemp works only on unicode in Python 3
-            tmpdir = tempfile.mkdtemp('', 'hgtests.', d and _strpath(d))
-            tmpdir = _bytespath(tmpdir)
+            tmpdir = tempfile.mkdtemp(b'', b'hgtests.', d)
 
         self._hgtmp = osenvironb[b'HGTMP'] = (
             os.path.realpath(tmpdir))