Replace the use of string.maketrans with something that can also work with Python3

xbob/extension/__init__.py

@@ -92,8 +92,15 @@ def pkgconfig(package):
   for k, v in kw.items(): # remove duplicated
     kw[k] = uniq(v)
 
+  try:
+    # Python 3 style
+    maketrans = ''.maketrans
+  except AttributeError:
+    # fallback for Python 2
+    from string import maketrans
+
   # adds version and HAVE flags
-  PACKAGE = package.upper().translate(string.maketrans(" -", "__"))
+  PACKAGE = package.upper().translate(maketrans(" -", "__"))
   kw['define_macros'] = [
       ('HAVE_%s' % PACKAGE, '1'),
       ('%s_VERSION' % PACKAGE, '"%s"' % version),