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 _globpatsplit(pat):
    """Split a glob pattern. Return a list.

    A naive version is "path.split("/")". This function handles more cases, like
    "{*,{a,b}*/*}".

    >>> _globpatsplit("*/**/x/{a,b/c}")
    ['*', '**', 'x', '{a,b/c}']
    """
    result = []
    buf = ""
    parentheses = 0
    for ch in pat:
        if ch == "{":
            parentheses += 1
        elif ch == "}":
            parentheses -= 1
        if parentheses == 0 and ch == "/":
            if buf:
                result.append(buf)
                buf = ""
        else:
            buf += ch
    if buf:
        result.append(buf)
    return result