Make setup python scripts 2/3 compatible

[markdewing]

Use print function in performance adjustment script.
Use items rather than iteritems in test_labels.

Addresses #1256

[prckent]

For reference, please add your Summit build recipe here. gcc or xlc, which modules? The versions in the manual are updated after the acceptance related upgrades. I assume gcc since xlc and the modules don't make finding the C++ library convenient. Using the gcc route for verification

[prckent]

Checked compatible between python2 and python3 on Summit. The anaconda provided python there should be consistent with other pythons on our other systems.

Of course this hints at wider issues. e.g. NEXUS is python2, we aren't controlling or testing our python environment.