Revert "Revert "Let virtualenv handle paths", and use $ENV_PATH more in hope of getting rid of bad interpreter errors."

That was not the problem. The problem is:

http://stackoverflow.com/questions/10813538/shebang-line-limit-in-bash-and-linux-kernel

This reverts commit 48568d93499bb73671080d26f86b005de10892f6.
Try to make shebangs shorter so that the won't be truncated by the kernel