testbrowser gives unhelpful errors

[Marius Gedminas]

Every now and then when something goes wrong (server error), zope.testbrowser gives this confusing error message instead:

Failed example:
    browser.getLink('Some link').click()
Exception raised:
    Traceback (most recent call last):
      File ".../zope3/src/zope/testing/doctest.py", line 1361, in __run
        compileflags, 1) in test.globs
      File "<doctest demo.txt[11]>", line 1, in ?
        abrowser.getLink('Print Ads').click()
      File ".../zope3/src/zope/testbrowser/browser.py", line 388, in click
        self.browser.mech_browser.follow_link(self.mech_link)
      File ".../zope3/src/mechanize/_mechanize.py", line 448, in follow_link
        return self.open(self.click_link(link, **kwds))
      File ".../zope3/src/mechanize/_mechanize.py", line 177, in open
        return self._mech_open(url, data)
      File ".../zope3/src/mechanize/_mechanize.py", line 217, in _mech_open
        self.set_response(response)
      File ".../zope3/src/mechanize/_mechanize.py", line 255, in set_response
        response = upgrade_response(response)
      File ".../zope3/src/mechanize/_mechanize.py", line 84, in upgrade_response
        data = get_data()
      File ".../zope3/src/mechanize/_util.py", line 426, in get_data
        return self.read(-1)
      File ".../zope3/src/mechanize/_util.py", line 444, in read
        self.__cache.write(self.wrapped.read())
      File ".../zope3/src/mechanize/_util.py", line 444, in read
        self.__cache.write(self.wrapped.read())
    TypeError: 'NoneType' object is not callable

I think I saw this one reported a while ago, but I cannot find the issue in the collector.

[Benji York (benji)]

I've seen this before, and have a vague feeling that I fixed it (or at least looked at it).

What version(s) of testbrowser do you see this in? Can you demonstrate how to reproduce it?

[Benji York (benji)]

I've narrowed this down to either a bug in mechanize or urllib2. I've checked in a work around to the trunk and 3.3 branch (revisions 69378 and 69379).

The problem arrises when the attempt to open a URI as the result of a redirect fails (returns an error HTTP status code). The mechanize/urllib2 data structures are in an unanticipated state and an attempt to read from a closed request triggers an exception (the one noted below).

I'll try to put together a pure mechanize test case and see what they think about it (unless someone beats me to it; hint, hint).

[Colin Watson (cjwatson)]

The zope.testbrowser project on Launchpad has been archived at the request of the Zope developers (see https://answers.launchpad.net/launchpad/+question/683589 and https://answers.launchpad.net/launchpad/+question/685285). If this bug is still relevant, please refile it at https://github.com/zopefoundation/zope.testbrowser.