This change suppresses the warning
warning: resource plugin aws is expected to have version >=0.11.3,
but has 0.11.1-dev-1523506162-g06ec765; the wrong version may
be on your path, or this may be a bug in the plugin
when the PULUMI_DEV envvar is set to a truthy value.
This warning keeps popping up in demos since I'm always using dev builds
and I'd like a way to shut it off, even though this can legitimately
point out a problem. Eventually I'll switch to official buildsa but,
until then, it seems worth having a simple way to suppress.