tortoiseHg crashes with segfault (qscintilla loads qt5 lib, not qt4)

[d9k]

see discussion at https://bitbucket.org/tortoisehg/thg/issues/4484/segfault-on-kubuntu-1604

When I try to execute and debug simple qt4 qscintilla program like http://eli.thegreenplace.net/2011/04/01/sample-using-qscintilla-with-pyqt debug stacktrace says `libQt5Core.so.5` is loaded instead of Qt4 core.

`$ apt-get install libqt4-dbg python-qt4-dbg libqscintilla2-12v5-dbg python-qscintilla2-dbg`

```
% gdb python
(gdb) run ./qscintilla-test.py
Starting program: /usr/bin/python ./qscintilla-test.py
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x00007fffefb1f225 in QMetaObject::className() const () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
(gdb) bt
#0 0x00007fffefb1f225 in QMetaObject::className() const () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#1 0x00007ffff046573f in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#2 0x00007ffff03ffed7 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#3 0x00007ffff7de74ea in call_init (l=<optimized out>, argc=argc@entry=2, argv=argv@entry=0x7fffffffd988, env=env@entry=0x7fffffffd9a0) at dl-init.c:72
#4 0x00007ffff7de75fb in call_init (env=0x7fffffffd9a0, argv=0x7fffffffd988, argc=2, l=<optimized out>) at dl-init.c:30
#5 _dl_init (main_map=main_map@entry=0xac8170, argc=2, argv=0x7fffffffd988, env=0x7fffffffd9a0) at dl-init.c:120
#6 0x00007ffff7dec712 in dl_open_worker (a=a@entry=0x7fffffffcd40) at dl-open.c:575
#7 0x00007ffff7de7394 in _dl_catch_error (objname=objname@entry=0x7fffffffcd30, errstring=errstring@entry=0x7fffffffcd38,
    mallocedp=mallocedp@entry=0x7fffffffcd2f, operate=operate@entry=0x7ffff7dec300 <dl_open_worker>, args=args@entry=0x7fffffffcd40) at dl-error.c:187
#8 0x00007ffff7debbd9 in _dl_open (file=0xa290a0 "/usr/lib/python2.7/dist-packages/PyQt4/Qsci.x86_64-linux-gnu.so", mode=-2147483646,
    caller_dlopen=0x521223 <_PyImport_GetDynLoadFunc+243>, nsid=-2, argc=<optimized out>, argv=<optimized out>, env=0x7fffffffd9a0) at dl-open.c:660
#9 0x00007ffff75edf09 in dlopen_doit (a=a@entry=0x7fffffffcf70) at dlopen.c:66
#10 0x00007ffff7de7394 in _dl_catch_error (objname=0xa2c3e0, errstring=0xa2c3e8, mallocedp=0xa2c3d8, operate=0x7ffff75edeb0 <dlopen_doit>,
    args=0x7fffffffcf70) at dl-error.c:187
#11 0x00007ffff75ee571 in _dlerror_run (operate=operate@entry=0x7ffff75edeb0 <dlopen_doit>, args=args@entry=0x7fffffffcf70) at dlerror.c:163
#12 0x00007ffff75edfa1 in __dlopen (file=<optimized out>, mode=<optimized out>) at dlopen.c:87
#13 0x0000000000521223 in _PyImport_GetDynLoadFunc () at ../Python/dynload_shlib.c:140
#14 0x0000000000520dcf in _PyImport_LoadDynamicModule () at ../Python/importdl.c:42
#15 0x00000000004aff2d in import_submodule.lto_priv () at ../Python/import.c:2722
#16 0x00000000004af6cd in load_next (p_buflen=<synthetic pointer>, buf=<optimized out>, p_name=<synthetic pointer>,
    altmod=<module at remote 0x7ffff7ea9910>, mod=<module at remote 0x7ffff7ea9910>) at ../Python/import.c:2537
#17 import_module_level.isra.3 (level=<optimized out>, fromlist=('QsciScintilla', 'QsciLexerPython'), globals=<optimized out>, name=<optimized out>)
    at ../Python/import.c:2254
#18 PyImport_ImportModuleLevel () at ../Python/import.c:2310
#19 0x00000000004b1418 in builtin___import__ () at ../Python/bltinmodule.c:49
#20 0x00000000004b1153 in PyObject_Call () at ../Objects/abstract.c:2546
#21 0x00000000004ce940 in PyEval_CallObjectWithKeywords () at ../Python/ceval.c:4219
#22 0x00000000004c773f in PyEval_EvalFrameEx () at ../Python/ceval.c:2622
#23 0x00000000004c2e05 in PyEval_EvalCodeEx () at ../Python/ceval.c:3582
#24 0x00000000004c2ba9 in PyEval_EvalCode (co=<optimized out>, globals=<optimized out>, locals=<optimized out>) at ../Python/ceval.c:669
#25 0x00000000004f20ef in run_mod.lto_priv () at ../Python/pythonrun.c:1376
#26 0x00000000004eca72 in PyRun_FileExFlags () at ../Python/pythonrun.c:1362
#27 0x00000000004eb1f1 in PyRun_SimpleFileExFlags () at ../Python/pythonrun.c:948
#28 0x000000000049e18a in Py_Main () at ../Modules/main.c:640
#29 0x00007ffff7811830 in __libc_start_main (main=0x49daf0 <main>, argc=2, argv=0x7fffffffd988, init=<optimized out>, fini=<optimized out>,
    rtld_fini=<optimized out>, stack_end=0x7fffffffd978) at ../csu/libc-start.c:291
#30 0x000000000049da19 in _start ()

```

I didn't mess with qt packages manually. I just upgraded kubuntu with simple commands

```
sudo do-release-upgrade -d
sudo apt-get dist-upgrade
sudo apt-get upgrade
reboot
```

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: tortoisehg 3.7.3-1
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CurrentDesktop: KDE
Date: Wed Apr 27 23:29:08 2016
InstallationDate: Installed on 2014-06-03 (693 days ago)
InstallationMedia: Kubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.1)
PackageArchitecture: all
SourcePackage: tortoisehg
UpgradeStatus: Upgraded to xenial on 2016-04-23 (4 days ago)