As previously written, if codeql finds a `Pipfile`, but no `Pipfile.lock`, it will run `pipenv install` with args that require `Pipfile.lock` to exist. Pipfile will fail with this message:
```
Usage: python -m pipenv install [OPTIONS] [PACKAGES]...
ERROR:: Pipfile.lock must exist to use --keep-outdated!
package installation with pipenv failed, see error above
```
This changeset enables auto_install to work with Pipfile when there is no lock. (Bonus: `--skip-lock` is generally a bit faster.)