All scripts in libexec/ (excluding pyenv) are called through pyenv,
therefore the shebang lines are not necessary. On some systems this
provides a measurable increase in performance of the shell prompt.
Related to pyenv/pyenv-virtualenv#259
I was seeing the following occasionally in scripts:
> …/.pyenv/libexec/pyenv-version-file-read: line 12: type: write error: Broken pipe
This patch hopefully improves/fixes this, and it seems better anyway to
just use sed here.