Unlike PyInstaller, pyenv doesn't leave backups of original env vars
when it modifies them. If we look into the shim, pyenv and pyenv-exec,
we can figure out that the PATH is modified like this:
PATH=$PYENV_BIN_PATH:${bin_path}:${plugin_bin}:$PATH
where
PYENV_BIN_PATH - starts with $PYENV_ROOT, see pyenv-exec source code.
bin_path - might not start with $PYENV_ROOT as it runs realpath on
it, see pyenv source code.
plugin_bin - might contain more than 1 entry, which start with
$PYENV_ROOT, see pyenv source code.
So having this, we can make a rightful assumption about what parts of the PATH
we need to remove in order to get the original PATH.
Fixes#2506
Ruslan Kuprieiev
pared