rss_rc action: use write instead of _write

[pabs3]

_write was a private function of the RssGenerator class while
.write is a public function that still exists.

Fixes: https://bugs.debian.org/787583
Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/werkzeug/wsgi.py", line 588, in call
return self.app(environ, start_response)
File "/usr/lib/python2.7/dist-packages/MoinMoin/wsgiapp.py", line 264, in call
response = run(context)
File "/usr/lib/python2.7/dist-packages/MoinMoin/wsgiapp.py", line 89, in run
response = dispatch(request, context, action_name)
File "/usr/lib/python2.7/dist-packages/MoinMoin/wsgiapp.py", line 137, in dispatch
response = handle_action(context, pagename, action_name)
File "/usr/lib/python2.7/dist-packages/MoinMoin/wsgiapp.py", line 203, in handle_action
handler(context.page.page_name, context)
File "/usr/lib/python2.7/dist-packages/MoinMoin/action/rss_rc.py", line 178, in execute
handler._write(
AttributeError: RssGenerator instance has no attribute '_write'

[ThomasWaldmann]

Related: #25

Since you are fixing a 5y old bug that likely only happened on very old versions of python 2.7, I'ld rather first see if it happens with recent 2.7.x versions.

[pabs3]

This crash still happened every day on wiki.debian.org with Debian buster's Python 2.7.16. It looks like the reason it still happened for us is that we were keeping around an ancient copy of PyXML/python-xml. The reason we did that was that one point python-xml got removed from Debian and the MoinMoin DocBoot export functionality stopped working. Since then it appears that PyXML has been merged into Python stdlib so we don't have to use it any more. I've now dropped our python-xml copy. Using private class member functions is probably not a good idea in any case so I still think this should be changed. BTW: when you concluded in #25 that the issue was fixed, it would have been helpful to forward that status back to Debian#787583 so that we would have dropped our copy of python-xml.

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-- bye, pabs https://wiki.debian.org/PaulWise

[ThomasWaldmann]

@pabs3 thanks for analyzing the issue.

I agree about private members, but that fact is commonly known to developers so I suspect there was some reason to use that and not the more obvious (and also "public") .write().

So if we want to change that, we need to be rather sure it does not break in some other situation.
Guess the only way to do that is to dig into moin repo history about changes at that place in the code and also to compare .write to ._write.

If you want to do that, feel free - otherwise I would prefer not touching that code considering you could fix it by removing the old python-xml code.

About updating issues: I only maintain issues filed in the project's issue tracker (== here).

[pabs3]

It seems like the Moin VCS repositories was not properly converted from arch to mercurial and then not properly converted from mercurial to git so the history of the three repositories is disjointed. I've checked my local copy of the history of the mercurial and git repos and there is a 2013 commit that switches from handler._out.write to handler._write with the commit message "fix python 2.7.5 compatibility". I don't have a copy of the arch repository. I suggest we just close this PR, it isn't useful to spend time on supporting ancient Python rather than Moin 2 and Python 3.

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-- bye, pabs https://wiki.debian.org/PaulWise