running `urllib.request.urlopen` multiple times causes the memory usage to increase with each run, even after calling `close()` on the request or using `del` on the result

To recreate this problem, run code:

    import urllib.request
    def ip():
        r = urllib.request.urlopen('https://api.ipify.org')
        b = r.read()
        r.close()
        print(len(b))
        return b

    for i in range(1000):
        result = ip()
        del result

Even though `len(b)` has a maximum value of 15 (for this url at least), the memory increases with each run by 200KB - 1MB