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 _execute_rpc_implementor_background(self, context, audit_name, target,
                                           response_queue, args, kwargs):
        """
        Honor a remote procedure call request from a plugin,
        from a background thread. Must only be used as the entry
        point for said background thread!

        :param context: Plugin execution context.
        :type context: PluginContext

        :param audit_name: Name of the audit requesting the call.
        :type audit_name: str

        :param target: RPC implementor function.
        :type target: callable

        :param response_queue: Response queue identity.
        :type response_queue: str

        :param args: Positional arguments to the call.
        :type args: tuple

        :param kwargs: Keyword arguments to the call.
        :type kwargs: dict
        """
        Config._context = context
        self.execute_rpc_implementor(
            audit_name, target, response_queue, args, kwargs)