Python 3.7 is not preinstalled on Kokoro images for macOS and Windows yet, therefore we fetch and install it in our prepare script. We currently only do that for 64-bit version of Python 3.7 on Windows.

This issue tracks a work item to add a 32-bit Python3.7 entry to the list of artifact targets after Kokoro image comes preinstalled with Python 3.7.

disposition/on hold: pending Kokoro image supplying Python 3.7