misc: Update #!env calls for python to explicit version

In some newer Linux distributions, env python default to Python 3.0. This
patch explicitly uses "python2" instead of just "python" for all scripts
that use #!

Reported-by: Sanchayan Maity <maitysanchayan@gmail.com>
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>

ext/ply/example/classcalc/calc.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 # -----------------------------------------------------------------------------
 # calc.py

ext/ply/example/newclasscalc/calc.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 # -----------------------------------------------------------------------------
 # calc.py