setuptools doesn't replace shebang from build directory when installing

• Pip version: 8.1.1
• Python version: 2.6
• Operating System: CentOS 6

Description:

I have a small python module with some scripts that I run in a virtual environment. My Makefile looks like this:

default: build

.DEFAULT:
    ./setup.py $@

build:
    ./setup.py build

/path/to/venv/bin/activate:
    virtualenv --system-site-packages /path/to/venv

install: /path/to/venv/bin/activate
    /path/to/venv/bin/pip install .

Now if I have a fresh install and run make install everything works great, and at the top of all of my scripts in $VENV/bin I have the following shebang:

#!/path/to/venv/bin/python

but if I first run make build and then make install then I get the system python in the shebang:

#!/usr/bin/python

I guess I would have expected the setup process to check and replace the shebang to the virtual environment's python.

Reproduce the issue with the mentioned Makefile, setup.py, and /path/to/venv/bin/pip install .: compare a fresh install with one after make build. Inspect the build and install entry points that handle script shebangs, then verify that installed scripts retain the virtual environment's Python path after both workflows.