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 unban_user(user_id=None):
    if not Permission(CanBanUser, identity=current_user):
        flash(_("You do not have the permissions to unban this user."),
              "danger")
        return redirect(url_for("management.overview"))

    # ajax request
    if request.is_xhr:
        ids = request.get_json()["ids"]

        data = []
        for user in User.query.filter(User.id.in_(ids)).all():
            if user.unban():
                data.append({
                    "id": user.id,
                    "type": "unban",
                    "reverse": "ban",
                    "reverse_name": _("Ban"),
                    "reverse_url": url_for("management.ban_user",
                                           user_id=user.id)
                })

        return jsonify(
            message="{} users unbanned.".format(len(data)),
            category="success",
            data=data,
            status=200
        )

    user = User.query.filter_by(id=user_id).first_or_404()

    if user.unban():
        flash(_("User is now unbanned."), "success")
    else:
        flash(_("Could not unban user."), "danger")

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