py3: use b'%d' to convert int to bytes instead of str()

Differential Revision: https://phab.mercurial-scm.org/D3280

hgext/convert/git.py

@@ -372,7 +372,7 b' class convert_git(common.converter_sourc'
 
         tzs, tzh, tzm = tz[-5:-4] + "1", tz[-4:-2], tz[-2:]
         tz = -int(tzs) * (int(tzh) * 3600 + int(tzm))
-        date = tm + " " + str(tz)
+        date = tm + " " + (b"%d" % tz)
         saverev = self.ui.configbool('convert', 'git.saverev')
 
         c = common.commit(parents=parents, date=date, author=author,