py3: make util.datapath a bytes variable

In this patch we make util.datapath a bytes variable, but we have to pass a
unicode to gettext.translation otherwise it will cry. Used pycompat.fsdecode()
to decode it back to unicode as it was converted to bytes using
pycompat.fsencode().

mercurial/i18n.py

@@ -49,6 +49,7 b" if (os.name == 'nt'"
 _ugettext = None
 
 def setdatapath(datapath):
+    datapath = pycompat.fsdecode(datapath)
     localedir = os.path.join(datapath, pycompat.sysstr('locale'))
     t = gettextmod.translation('hg', localedir, _languages, fallback=True)
     global _ugettext

mercurial/util.py

@@ -938,6 +938,9 b" if mainfrozen() and getattr(sys, 'frozen"
 else:
     datapath = os.path.dirname(__file__)
 
+if not isinstance(datapath, bytes):
+    datapath = pycompat.fsencode(datapath)
+
 i18n.setdatapath(datapath)
 
 _hgexecutable = None