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 insert_accented(self, c, accent):
        if c.isalpha():
            if c.isupper():
                cap = 'capital'
            else:
                cap = 'small'
            try:
                c = lookup("latin %s letter %c with %s" % (cap, c, accent))
                self.insert(INSERT, c)
                # Prevent plain letter from being inserted too, tell Tk to
                # stop handling this event
                return "break"
            except KeyError, e:
                pass