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 test_reverse_iso8601_datetime():
    dates = [
        ("2011-01-01T00:00:00+00:00", datetime(2011, 1, 1, tzinfo=pytz.utc)),
        ("2011-01-01T23:59:59+00:00", datetime(2011, 1, 1, 23, 59, 59, tzinfo=pytz.utc)),
        ("2011-01-01T23:59:59.001000+00:00", datetime(2011, 1, 1, 23, 59, 59, 1000, tzinfo=pytz.utc)),
        ("2011-01-01T23:59:59+02:00", datetime(2011, 1, 1, 21, 59, 59, tzinfo=pytz.utc))
    ]

    for date_string, expected in dates:
        yield assert_equal, inputs.datetime_from_iso8601(date_string), expected