Update the executable used to run the examples to be the same as harn…

…ess.

In order to have an easy way to control which python runs the examples,
make the python version used into the one used by the harness itself.
That way if you invoke it with Python 3, it'll test with Python 3.

examples/run_all_examples.py

@@ -169,7 +169,7 @@ def main():
     any_failed = False
     for example in find_examples():
         print("Example: {}".format(example.name))
-        result = example.run(runs=args.runs)
+        result = example.run(python=sys.executable, runs=args.runs)
         result.show(indent='  ')
         if not args.keep:
             if result.fail_file: