Why has coverage been locked to `==4.0.3` for two years? Why not `>=4.0.0`?

If I add localstack to my pipenv, I can't lock because of this unnecessary dependency.
return json.loads(self.to_json())
    @classmethod
    def from_json(cls, j):
        j = JsonObject.as_dict(j)
        result = cls()
        result.apply_json(j)
        return result
    @classmethod
    def from_json_list(cls, l):
        return [cls.from_json(j) for j in l]
    @classmethod
    def as_dict(cls, obj):
        if isinstance(obj, dict):
            return obj
        return obj.to_dict()
    def __str__(self):
        return self.to_json()
    def __repr__(self):
        return self.__str__()
def is_string(s, include_unicode=True):
    if isinstance(s, str):
        return True
    if include_unicode and isinstance(s, six.text_type):
        return True
    return False
def md5(string):
    m = hashlib.md5()
    m.update(to_bytes(string))
    return m.hexdigest()
def in_ci():