This is required for the shims to handle `#!/usr/bin/env python3` in a
shebang, just like `python` is handled currently: it will set
`PYENV_DIR` to the root of the invoked script, which is required for a
`.python-version` script to get picked up from there.
This was rejected for rbenv, where it does not make much sense
(https://github.com/sstephenson/rbenv/pull/735).
Ref: https://github.com/yyuu/pyenv/pull/368#issuecomment-102806837
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.
With e.g. /usr/local/bin/.python-version owned by some user, `pyenv
local foo` would fail, if the user has no permissions for
`/usr/local/bin`, but only the `.python-version` file.