def test_blocklist_fatal(self):
        """test 'pip install <blocklisted-fatal-package>'."""
        output = self.run_command("pip --verbose install pip", exitcode=1)
        self.assertIn("StaSh uses a custom version of PIP", output)
        self.assertIn("PackageBlocklisted", output)
        self.assertNotIn("Package installed: pip", output)
test 'pip install <blocklisted-fatal-package>'.
tests/pip/test_pip.py