Quotes around hashbangs are not recognised and are considered invalid syntax, at least on Bash on OS X 10.12. There's really no workaround (that I'm aware of) for paths containing spaces, except maybe symlinking the directory in the path the contains the space. Maybe a warning message about this would be best.

To reproduce this issue, simply run the following from an empty directory that has a space in its path:

```
pyenv venv/
source ./venv/bin/activate
pip
```

The result should be something like:
```
-bash: /Users/me/dir with space/foo/venv/bin/pip: "/Users/me/dir: bad interpreter: No such file or directory
```