When sourcing the activate script from bash, $PATH is restored from 
$_OLD_VIRTUAL_PATH.  If bash was invoked from fish (e.g. when running a shell script), and a virtualenv was activated from fish via activate.fish, the 
$_OLD_VIRTUAL_PATH will contain path separated by the ascii record separator char (chr(30)), since this is how the fish shell stores arrays.

But the activate script for bash will then set $PATH to $_OLD_VIRTUAL_PATH, which breaks most bash scripts.

Instead the activate scripts should differentiate between

$_OLD_BASH_VIRTUAL_PATH
and
$_OLD_FISH_VIRTUAL_PATH

or the activate.fish should take care to replace chr(30) with colons before it sets $_OLD_VIRTUAL_PATH.


bash$ pyvenv my-venv
bash$ fish
fish$ . my-venv/bin/activate.fish
fish$ bash
bash$ . my-venv/bin/activate
# $PATH is now broken, since it contains record separators instead of colons to separate paths

A work around is to unset the _OLD_VIRTUAL_PATH variable before the activate:

set -e _OLD_VIRTUAL_PATH