protected CookieAttributeHandler getAttribHandler(final String name) {
        final CookieAttributeHandler handler = findAttribHandler(name);
        Asserts.check(handler != null, "Handler not registered for " +
                name + " attribute");
        return handler;
    }
Gets attribute handler {@link CookieAttributeHandler} for the
given attribute.

@param name attribute name. e.g. Domain, Path, etc.
@throws IllegalStateException if handler not found for the
         specified attribute.
httpclient5/src/main/java/org/apache/hc/client5/http/impl/cookie/AbstractCookieSpec.java