hostkeymap: Fix sanitize_keymap on python3

And add test cases to cover the failure

https://bugzilla.redhat.com/show_bug.cgi?id=1585574

tests/hostkeymap.py

@@ -40,3 +40,11 @@ class TestHostkeymap(unittest.TestCase):
                 hostkeymap._xorg_keymap(
                     _open("xorg-rhel5.txt")),
                 "us")
+
+    def testSanitize(self):
+        def san(inp):
+            return hostkeymap.sanitize_keymap(inp)
+
+        self.assertEqual(san("pt"), "pt")
+        self.assertEqual(san("de-us"), "de")
+        self.assertEqual(san("en_us"), "en-us")

virtinst/hostkeymap.py

@@ -186,11 +186,8 @@ def sanitize_keymap(kt):
     # Try a more intelligent lookup: strip out all '-' and '_', sort
     # the keytable keys putting the longest first, then compare
     # by string prefix
-    def len_cmp(a, b):
-        return len(b) - len(a)
-
     clean_kt = kt.replace("-", "").replace("_", "")
-    sorted_keys = sorted(list(keytable.keys()), len_cmp)
+    sorted_keys = sorted(list(keytable.keys()), key=len)
 
     for key in sorted_keys:
         origkey = key