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 _get_unique_constraints(self, table):
    """Retrieve information about existing unique constraints of the table

    This feature is needed for _recreate_table() to work properly.
    Unfortunately, it's not available in sqlalchemy 0.7.x/0.8.x.

    """

    data = table.metadata.bind.execute(
        """SELECT sql
           FROM sqlite_master
           WHERE
               type='table' AND
               name=:table_name""",
        table_name=table.name
    ).fetchone()[0]

    UNIQUE_PATTERN = "CONSTRAINT (\w+) UNIQUE \(([^\)]+)\)"
    return [
        UniqueConstraint(
            *[getattr(table.columns, c.strip(' "')) for c in cols.split(",")],
            name=name
        )
        for name, cols in re.findall(UNIQUE_PATTERN, data)
    ]