Prepare an already-installed requirement

def prepare_installed_requirement(self, req, require_hashes, skip_reason):
        # type: (InstallRequirement, bool, Optional[str]) -> DistAbstraction
        """Prepare an already-installed requirement
        """
        assert req.satisfied_by, "req should have been satisfied but isn't"
        assert skip_reason is not None, (
            "did not get skip reason skipped but req.satisfied_by "
            "is set to %r" % (req.satisfied_by,)
        )
        logger.info(
            'Requirement %s: %s (%s)',
            skip_reason, req, req.satisfied_by.version
        )
        with indent_log():
            if require_hashes:
                logger.debug(
                    'Since it is already installed, we are trusting this '
                    'package without checking its hash. To ensure a '
                    'completely repeatable environment, install into an '
                    'empty virtualenv.'
                )
            abstract_dist = Installed(req)

        return abstract_dist