Do HTTPError objects always have a read method?

[Steven D'Aprano]

I understood that HTTPError objects always have a read method, so they 
can be treated as if they were a webpage. E.g. something like this 
simplified snippet:


address = 'http://www.yahoo.com/spamspamspamspamspam'
try:
    conn = urllib2.urlopen(address)
except urllib2.HTTPError, e:
    conn = e
print conn.read()  # Print the requested page, or the error page.



But in the source code to urllib2 (Python 2.5):


class HTTPError(URLError, addinfourl):
    """Raised when HTTP error occurs, but also acts like non-error 
return"""
    __super_init = addinfourl.__init__

    def __init__(self, url, code, msg, hdrs, fp):
        self.code = code
        self.msg = msg
        self.hdrs = hdrs
        self.fp = fp
        self.filename = url
        # The addinfourl classes depend on fp being a valid file
        # object.  In some cases, the HTTPError may not have a valid
        # file object.  If this happens, the simplest workaround is to
        # not initialize the base classes.
        if fp is not None:
            self.__super_init(fp, hdrs, url)

    def __str__(self):
        return 'HTTP Error %s: %s' % (self.code, self.msg)



That tells me that HTTPError objects aren't guaranteed to include a file-
like interface. That makes me unhappy.

Under what circumstances do HTTPError objects not have a valid file 
object? How common is this? Does anyone have an example of a URL that 
fails in that fashion?



Thank you,



-- 
Steven