def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
async def print_debug(loop):
    while True:
        print(chr(27) + "[2J")  # clear screen
        loop.print_debug_info()
        await asyncio.sleep(0.5)