As with the previous similar changes, this is intended to catch
problems as they happen instead of ignoring them and continuing on
to potentially fail later. Setting this on all existing scripts
will allow us to enforce use via Jenkins.
Change-Id: Iad2d490c86dceab148ea9ab08f457c49a5d5352e
Using a custom pypi mirror can be very convenient, making image builds
substantially faster - because we create multiple virtual
environments we benefit more than single-virtualenv users would.
Change-Id: I997daf1f9477c447e1fb30818aea9e80a49b31a6