Don't call next() method in CSV reader

The next() method was renamed in python3. Simply avoid calling
it to ensure portability

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

tools/keymap-gen

diff --git a/tools/keymap-gen b/tools/keymap-gen
index 5dc7d3d..3ed4b99 100755
--- a/tools/keymap-gen
+++ b/tools/keymap-gen
@@ -143,13 +143,17 @@
     def load(self, filename):
         self._generate_checksum(filename)
 
-        with open(filename, 'rb') as f:
+        with open(filename, 'r') as f:
             reader = csv.reader(f)
 
-            # Discard column headings
-            reader.next()
+            first = True
 
             for row in reader:
+                # Discard column headings
+                if first:
+                    first = False
+                    continue
+
                 # We special case MAP_LINUX since that is out
                 # master via which all other mappings are done
                 linux = self.load_linux(row)