Ubuntu 12.04 LTS reached its regular End of Life on April 28, 2017.
Depends-On: I5e145095a10db112bb27516bfe652d2cdc052a61
Change-Id: I64af4c5183d77a75dcd062895d19b0a1330c8da8
Currently we install pip/virtualenv with "/usr/local/bin/dib-python".
This means that every time you create a virtualenv, the python
interpreter inside it is called "dib-python" which is confusing.
Add an env var DIB_PYTHON that points directly the to interpreter
available during build, for use when running scripts.
Change-Id: I88ad3c9eb958d58db4631d9b27bc2c592f970345
