py3: use pycompat.bytestr() on extra values because it can be int

One such example is {'close': 1} which marks a branch as closed.

This makes test-convert-mtn.t pass on Python 3.

Differential Revision: https://phab.mercurial-scm.org/D5864

contrib/python3-whitelist

@@ -121,6 +121,7 b' test-convert-git.t'
 test-convert-hg-sink.t
 test-convert-hg-source.t
 test-convert-hg-startrev.t
+test-convert-mtn.t
 test-convert-splicemap.t
 test-convert-svn-sink.t
 test-convert-tagsbranch-topology.t

mercurial/changelog.py

@@ -70,7 +70,10 b' def decodeextra(text):'
 
 def encodeextra(d):
     # keys must be sorted to produce a deterministic changelog entry
-    items = [_string_escape('%s:%s' % (k, d[k])) for k in sorted(d)]
+    items = [
+        _string_escape('%s:%s' % (k, pycompat.bytestr(d[k])))
+        for k in sorted(d)
+    ]
     return "\0".join(items)
 
 def stripdesc(desc):