John has a more elegant response to this same question here:
http://askubuntu.com/questions/764610/how-to-install-snap-packages-behind-web-proxy-on-ubuntu-16-04/773230#773230
John has a more elegant response to this same question here:
http:// askubuntu. com/questions/ 764610/ how-to- install- snap-packages- behind- web-proxy- on-ubuntu- 16-04/773230# 773230