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)
def _get_markup_for_tags(self, tag_names):
        """Given a list of tags names, generates the pango markup to render
         that list with the tag colors used in GTG

        @param tag_names: the list of the tags (strings)
        @return str: the pango markup string
        """
        if ALLTASKS_TAG in tag_names:
            tags_txt = ""
        else:
            tags_txt = get_colored_tags_markup(self.req, tag_names)
        return "<small>" + tags_txt + "</small>"