Get the pip version in the environment.  Useful for knowing which args we can use
        when installing.

def pip_version(self):
        """
        Get the pip version in the environment.  Useful for knowing which args we can use
        when installing.
        """
        from .vendor.packaging.version import parse as parse_version
        pip = next(iter(
            pkg for pkg in self.get_installed_packages() if pkg.key == "pip"
        ), None)
        if pip is not None:
            pip_version = parse_version(pip.version)
        return parse_version("18.0")