Fix: Py2 exec polyfill
Fix: Py2 exec polyfill

The actual call to exec was missing in the polyfill... It has now
been added.

Signed-off-by: Kevin Conway <3473c1f185ca03eadc40ad288d84425b54fd7d57@gmail.com>

rackerlabs/PyPerf,kevinconway/PyPerf,rackerlabs/PyPerf,kevinconway/PyPerf,rackerlabs/PyPerf,kevinconway/PyPerf