def install_pip(self, package, save=True, save_dev=False):
        """Installs a pip package.

        :param save: if `True`, pins the package to the Hydrogen requirements
            YAML file.
        :param save_dev: if `True`, pins the package as a development
            dependency to the Hydrogen requirements YAML file.
        :param return: a **single** :class:`Requirement` object, representing
            the installed version of the given package.
        """
        requirement = Requirement.coerce(package)
        click.echo("pip install " + requirement.package)
        cmd = envoy.run("pip install {}".format(str(requirement)))
        if cmd.status_code == 0:
            installed_packages = get_installed_pypackages()
            package = installed_packages[requirement.package]
            requirement.version = "=={}".format(package.version)
            if save:
                self.requirements["all"].add(requirement)
            if save_dev:
                self.requirements["dev"].add(requirement)
            if save or save_dev:
                self.requirements.save()
            return requirement
        else:
            fatal(cmd.std_err)
def refresh(self):
        """refreshes the Gtk.Liststore"""
        self.backendid_to_iter = {}
        self.liststore.clear()

        # Sort backends
        # 1, put default backend on top
        # 2, sort backends by human name
        backends = list(self.req.get_all_backends(disabled=True))
        backends = sorted(backends,
                          key=lambda backend: (not backend.is_default(),
                                               backend.get_human_name()))

        for backend in backends:
            self.add_backend(backend)
            self.on_backend_state_changed(None, backend.get_id())