matplotlib 1.5.0~rc2-1ubuntu2: autopkgtest failures on all architectures, SIGBUS in python2.7-dbg

The matplotlib 1.5.0~rc2-1ubuntu2 package is not migrating from xenial-proposed to xenial because its autopkgtests are now failing on all architectures.

adt-run [10:26:22]: test qt4agg: [-----------------------
=== Qt4Agg ===
=== python2.7 ===
=== python2.7-dbg ===
Bus error (core dumped)
adt-run [10:26:36]: test qt4agg: -----------------------]
adt-run [10:26:36]: test qt4agg: - - - - - - - - - - results - - - - - - - - - -
qt4agg FAIL non-zero exit status 135

This test failure is reproducible for me locally.

Running the test program under gdb, I get the following backtrace:

Program received signal SIGBUS, Bus error.
sipOMFindObject (om=<optimized out>, key=<optimized out>, td=<optimized out>)
    at /build/sip4-FuZUrT/sip4-4.17+dfsg/siplib/objmap.c:135
135 /build/sip4-FuZUrT/sip4-4.17+dfsg/siplib/objmap.c: No such file or directory.
(gdb) bt
#0 sipOMFindObject (om=<optimized out>, key=<optimized out>,
    td=<optimized out>)
    at /build/sip4-FuZUrT/sip4-4.17+dfsg/siplib/objmap.c:135
#1 0x00007fffee7dbc92 in release_QApplication (sipCppV=0x138e7f0)
    at /build/python-qt4-DPZMhZ/python-qt4-4.11.4+dfsg/sip/QtGui/qapplication.sip:1004
#2 0x00007fffefe8f699 in forgetObject (sw=sw@entry=0x7fffeb32d6a0)
    at siplib.c:11135
#3 0x00007fffefe90d59 in sipWrapper_dealloc (self=0x7fffeb32d6a0)
    at siplib.c:10702
#4 0x00000000004b415d in subtype_dealloc (
    self=<QApplication at remote 0x7fffeb32d6a0>)
    at ../Objects/typeobject.c:1030
#5 0x000000000048fca2 in _Py_Dealloc (
    op=<QApplication at remote 0x7fffeb32d6a0>) at ../Objects/object.c:2262
#6 0x000000000048019e in insertdict_by_entry (mp=0x7ffff03c51a8, key='qApp',
    hash=8297207904849122534, ep=0x1809e58, value=None)
    at ../Objects/dictobject.c:519
#7 0x0000000000480444 in insertdict (mp=0x7ffff03c51a8, key='qApp',
    hash=8297207904849122534, value=None) at ../Objects/dictobject.c:556
#8 0x0000000000480d7a in dict_set_item_by_hash_or_entry (
    op=<unknown at remote 0x180a630>, key='qApp', hash=8297207904849122534,
    ep=0x0, value=None) at ../Objects/dictobject.c:765
---Type <return> to continue, or q <return> to quit---
#9 0x0000000000480f00 in PyDict_SetItem (op=
    {'_create_qApp': None, 'cursord': None, 'TimerQT': None, 'draw_if_interactive': None, 'Gcf': None, 'unicode_literals': None, 'SHIFT': None, 'absolute_import': None, 'QtWidgets': None, 'ShowBase': None, 'cursors': None, 'FigureManager': None, 'unichr': None, 'SubplotToolQt': None, 'is_string_like': None, 'MainWindow': None, 'FigureCanvasBase': None, 'QtGui': None, 'FigureManagerBase': None, 'FigureCanvas': None, 'six': None, 'FigureCanvasQT': None, '__package__': None, 're': None, 'show': None, 'fn_name': None, '__version__': None, '__doc__': None, 'exception_handler': None, 'division': None, 'CTRL': None, 'new_figure_manager_given_figure': None, 'SubplotTool': None, 'MODIFIER_KEYS': None, '__builtins__': {'bytearray': <type at remote 0x8afd40>, 'IndexError': <type at remote 0x8b63e0>, 'all': <built-in function all>, 'help': <_Helper at remote 0x7ffff7e73ed0>, 'vars': <built-in function vars>, 'SyntaxError': <type at remote 0x8b5d60>, 'unicode': <type at remote 0x8cd4e0>, 'UnicodeDecodeError': <type at remote ...(truncated), key='qApp', value=None) at ../Objects/dictobject.c:818
#10 0x000000000048a888 in _PyModule_Clear (m=<module at remote 0x7ffff00be4d8>)
    at ../Objects/moduleobject.c:139
#11 0x000000000054ad5b in PyImport_Cleanup () at ../Python/import.c:530
#12 0x000000000055e4ab in Py_Finalize () at ../Python/pythonrun.c:458
#13 0x000000000057b456 in Py_Main (argc=2, argv=0x7fffffffe3c8)
    at ../Modules/main.c:665
#14 0x0000000000418066 in main (argc=2, argv=0x7fffffffe3c8)
    at ../Modules/python.c:23

This backtrace points to a possible problem with python-sip. There is a new version of python-sip in xenial vs. wily, however the bug is not reproducible with xenial python-sip{,-dbg} and xenial matplotlib, only with the xenial-proposed matplotlib.