Why does setuptools need to write bytecode?

Question

If you try to run virtualenv with the environmental variable PYTHONDONTWRITEBYTECODE=true set, it gives this error:

The PYTHONDONTWRITEBYTECODE environment variable is not compatible with setuptools. Either use --distribute or unset PYTHONDONTWRITEBYTECODE.

Why does setuptools require the ability to write bytecode?

I don't particularly like having .pyc files around, so I like to prevent it from being written.

(I'm not asking how to get around this; that's trivial: just add PYTHONDONTWRITEBYTECODE="" at the beginning of any command that requires the flag to be unset, or unset it globally)

Answer 1

Use a recent version of virtualenv and you will not see this error.