Add script for Python 3 compat checks.

meta/check-py3k.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+# Check Python sources for Python 3 compatibility using pylint.
+#
+# Install pylint with 'pip install pylint'.
+cd $(dirname "$0")
+pylint --py3k --reports=no -- *.py cretonne isa