This patch set adds in -E flag for ``sudo pip install`` so
any environment variable is preserved for the install. This
allows for some proxy-related variables such as ``http_proxy``
to pass through for pip.
This mirrors the change in [0].
[0] https://review.openstack.org/#/c/531270/1
Change-Id: Ib513fce862f31d784634645ac6b038c6a35f4cd6