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 rename_source(self):
        """This is fairly horrible.
        The github tarfiles have weird names that do not correspond to the
        canonical name. We need to rename these, but leave a symlink for
        spack to work with.
        """
        # Note that this particular OpenFOAM requires absolute directories
        # to build correctly!
        parent   = os.path.dirname(self.stage.source_path)
        original = os.path.basename(self.stage.source_path)
        target   = 'OpenFOAM-{0}'.format(self.version)
        # Could also grep through etc/bashrc for WM_PROJECT_VERSION
        with working_dir(parent):
            if original != target and not os.path.lexists(target):
                os.rename(original, target)
                os.symlink(target, original)
                tty.info('renamed {0} -> {1}'.format(original, target))