Fix Version/s: None
Some systems require the HTTP(S)_PROXY environment variables to be set when making internet connections. sconsUtils does not currently forward these environment variables to the test environment and so this can lead to tests failing or hanging. This can happen in science pipelines tests at USDF when triggering a download of the IERS tables inside astropy.
Forwarding these variables seems generally useful even if the USDF no longer needs them.
Can't see a down side to merging this. Approved.