[PATCH] Fix TestPkgRelations failures with python3.

[Stuart Prescott]

Hi John,

An impressive puzzle!

> At the commit before this one, I consistently get this error:
> 
> $ python3 test_deb822.py
> ..................................................E.
> 
======================================================================
> ERROR: test_packages (__main__.TestPkgRelations)
> ----------------------------------------------------------------------
> Traceback (most recent call last):
>   File "test_deb822.py", line 1051, in test_packages
>     "foo bar")
>   File "/usr/lib/python3.4/unittest/case.py", line 735, in assertWarns
>     return context.handle('assertWarns', callable_obj, args, kwargs)
>   File "/usr/lib/python3.4/unittest/case.py", line 161, in handle
>     with self:
>   File "/usr/lib/python3.4/unittest/case.py", line 205, in __enter__
>     for v in sys.modules.values():
> RuntimeError: dictionary changed size during iteration
> 
> ----------------------------------------------------------------------
> Ran 52 tests in 0.553s
> 
> FAILED (errors=1)

A quick search tells me this has come up a few times before with various other 
modules normally taking the blame for the behaviour, for instance:

	https://bitbucket.org/gutworth/six/issue/68/assertwarns-and-six

It looks like pydoc had this problem too and this was solved by disabling the 
affected tests:

	http://bugs.python.org/issue20484
 
Perhaps case.py should be wrapping sys.modules.values() in a list() but I also 
can't see how walking over sys.modules.values() like this could cause the dict 
to be changed. That said, six does a lot of lazy loading of modules, but I 
don't know why this is different for you compared to me and ci.debian.net.

> It happens with both python3.3 (3.3.5-1) and python3.4 (3.4.1-10).  This
> is without a .pythonrc.py or any other local environment changes I can
> think of.


$ git checkout db4d5584e5833866c4c216d1a8772518e0d1451f

On my local machine (wheezy with lots and lots of stuff installed)

$ dpkg -l python3.2
ii  python3.2         3.2.3-7       amd64      Interactive high-level object
$ python3 test_deb822.py
....................................................
----------------------------------------------------------------------
Ran 52 tests in 0.665s

OK

In a not-particularly-clean sid schroot:

$ dpkg -l python3,4
ii  python3.4      3.4.1-10     amd64        Interactive high-level object-ori
$ python3 test_deb822.py
....................................................
----------------------------------------------------------------------
Ran 52 tests in 0.810s

In a very clean build schroot either manually or letting adt-run it:

# dpkg -l python3.4
ii  python3.4      3.4.1-10     amd64        Interactive high-level object-ori
# python3 test_deb822.py
....................................................
----------------------------------------------------------------------
Ran 52 tests in 0.682s


> I'm not yet sure how or why sys.modules changes size...  The workaround
> works because it avoids the code path that iterates over sys.

It seems very weird that this test should be iterating over sys in the first 
place.

> If it works for you with the latest python3 packages from sid, I'm even
> more confused.  Maybe some python3-foo library is doing something
> bizarre?  We could compare package lists.

Indeed ...it works for me with oldish sid packages and current sid packages.

Well a reasonable starting point for that would be to try it out in a clean 
chroot:

# http_proxy=http://localhost:3142/ debootstrap sid sid-amd64 
http://http.debian.net/debian
# cp -a .../python-debian/ sid-amd64/tmp
# chroot sid-amd64
# apt-get install python3 python3-apt python3-chardet python3-six
# cd /tmp/python-debian/tests
# python3 test_deb822.py
....................................................
----------------------------------------------------------------------
Ran 52 tests in 0.103s

There's very little python3 installed in that chroot at all at that stage:

# dpkg -l |grep python3 | awk '{print $2}'
libpython3-stdlib:amd64
libpython3.4-minimal:amd64
libpython3.4-stdlib:amd64
python3
python3-apt
python3-chardet
python3-minimal
python3-pkg-resources
python3-six
python3.4
python3.4-minimal


cheers
Stuart

-- 
Stuart Prescott    http://www.nanonanonano.net/   stuart at nanonanonano.net
Debian Developer   http://www.debian.org/         stuart at debian.org
GPG fingerprint    90E2 D2C1 AD14 6A1B 7EBB 891D BBC1 7EBB 1396 F2F7