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 enable_plugin(plugin):
    plugin = get_plugin_from_all(plugin)

    if plugin.enabled:
        flash(_("Plugin %(plugin)s is already enabled.", plugin=plugin.name),
              "info")
        return redirect(url_for("management.plugins"))

    try:
        plugin.enable()
        flash(_("Plugin %(plugin)s enabled. Please restart FlaskBB now.",
                plugin=plugin.name), "success")
    except OSError:
        flash(_("It seems that FlaskBB does not have enough filesystem "
                "permissions. Try removing the 'DISABLED' file by "
                "yourself instead."), "danger")

    return redirect(url_for("management.plugins"))