[lmi] Can't get GUI test to run for pc-linux-gnu

[Greg Chicares]

I feel certain that lmi's GUI tests passed for pc-linux-gnu at
some time in the not-too-distant past, but now they fail for me:

NOTE: starting the test suite
Exception type: '(anonymous namespace)::test_assertion_failure_exception'
# 0 0x7f0b5579ef46: /opt/lmi/src/lmi/unwind.cpp:194 __cxa_throw
# 1 0x55ff10869a9b: /opt/lmi/src/lmi/main_wx_test.cpp:804 
SkeletonTest::OnAssertFailure(wchar_t co>
# 2 0x7f0b54bb2ffc: ???:0 wxDefaultAssertHandler(wxString const&, int, wxString 
const&, wxString c>
# 3 0x7f0b54bb0482: ???:0 wxOnAssert(char const*, int, char const*, char 
const*, wxString const&)
# 4 0x55ff108c6b31: /opt/lmi/local/include/wx-3.1/wx/testing.h:424 
wxTestingModalHook::Enter(wxDia>
# 5 0x7f0b54ee0d75: ???:0 wxModalDialogHook::CallEnter(wxDialog*)
# 6 0x7f0b54db8d19: ???:0 wxDialog::ShowModal()
# 7 0x7f0b55ae610d: /opt/lmi/src/lmi/skeleton.cpp:470 
Skeleton::UponAbout(wxCommandEvent&)
# 8 0x7f0b54cf1b9e: ???:0 
wxEvtHandler::ProcessEventIfMatchesId(wxEventTableEntryBase const&, wxEv>
# 9 0x7f0b54cf38d3: ???:0 wxEventHashTable::HandleEvent(wxEvent&, wxEvtHandler*)
#10 0x7f0b54cf3934: ???:0 wxEvtHandler::TryHereOnly(wxEvent&)
#11 0x7f0b54cf39b3: ???:0 wxEvtHandler::ProcessEventLocally(wxEvent&)
#12 0x7f0b54cf3a92: ???:0 wxEvtHandler::ProcessEvent(wxEvent&)
#13 0x7f0b54f284a1: ???:0 wxWindowBase::TryAfter(wxEvent&)
#14 0x7f0b54cf3bc0: ???:0 wxEvtHandler::SafelyProcessEvent(wxEvent&)
#15 0x7f0b54edf840: ???:0 wxMenuBase::DoProcessEvent(wxMenuBase*, wxEvent&, 
wxWindow*)
#16 0x7f0b54edfab1: ???:0 wxMenuBase::SendEvent(int, int)
[...snip many lines...]
#77 0x55ff108716ea: ???:0 _start

I think that's just saying that an exception wasn't caught,
and the output continues:

Exception type: 'std::runtime_error'
# 0 0x7f0b5579ef46: /opt/lmi/src/lmi/unwind.cpp:194 __cxa_throw
# 1 0x55ff108c0c6a: /opt/lmi/src/lmi/main_wx_test.cpp:773 
SkeletonTest::RethrowStoredException()
# 2 0x7f0b54be486e: ???:0 wxEventLoopBase::YieldFor(long)
# 3 0x7f0b54d296dd: ???:0 (anonymous 
namespace)::wxUIActionSimulatorXTestImpl::DoX11Key(unsigned c>
# 4 0x7f0b54f21ac6: ???:0 wxUIActionSimulator::Key(int, int, bool)
# 5 0x7f0b54f21b81: ???:0 wxUIActionSimulator::Char(int, int)
# 6 0x55ff108c8f74: /opt/lmi/src/lmi/wx_test_about_version.cpp:262 
wx_test_case_about_dialog_versi>
# 7 0x55ff108c3ea3: /opt/lmi/src/lmi/main_wx_test.cpp:216 
SkeletonTest::RunTheTests()
# 8 0x7f0b54cf3971: ???:0 wxEvtHandler::TryHereOnly(wxEvent&)
# 9 0x7f0b54cf39b3: ???:0 wxEvtHandler::ProcessEventLocally(wxEvent&)
#10 0x7f0b54cf3a92: ???:0 wxEvtHandler::ProcessEvent(wxEvent&)
#11 0x7f0b54cf27ec: ???:0 wxEvtHandler::ProcessPendingEvents()
#12 0x7f0b54bb3407: ???:0 wxAppConsoleBase::ProcessPendingEvents()
#13 0x7f0b54d35fd1: ???:0 wxApp::DoIdle()
#14 0x7f0b54d360e3: ???:0 wxapp_idle_callback
#15 0x7f0b53114d6f: ???:0 g_main_context_dispatch
#16 0x7f0b53115118: ???:0 g_main_context_dispatch
#17 0x7f0b5311540b: ???:0 g_main_loop_run
#18 0x7f0b5392ab95: ???:0 gtk_main
#19 0x7f0b54d505e5: ???:0 wxGUIEventLoop::DoRun()
#20 0x7f0b54be43d6: ???:0 wxEventLoopBase::Run()
#21 0x7f0b54bb1427: ???:0 wxAppConsoleBase::MainLoop()
#22 0x55ff108c0e49: /opt/lmi/src/lmi/main_wx_test.cpp:724 SkeletonTest::OnRun()
#23 0x7f0b54c2bef6: ???:0 wxEntry(int&, wchar_t**)
#24 0x55ff10870e58: /opt/lmi/src/lmi/main_wx_test.cpp:957 main
#25 0x7f0b5442bd0a: ../csu/libc-start.c:308 __libc_start_main
#26 0x55ff108716ea: ???:0 _start
Abnormal-termination handler called. Please report this problem.

Vadim--Have you seen this? Would the Skeleton::UponAbout() GUI test
be the right place for me to start looking?

Has this ever worked yet on github? I find CI results here:
  https://github.com/let-me-illustrate/lmi/actions
and the most recent run is here:
  
https://github.com/let-me-illustrate/lmi/runs/2133646829?check_suite_focus=true
but the circle-with-diagonal-line icon (and the "0s" timing)
suggests failure. The outcome looks the same here, 20 days ago,
which looks like the oldest CI run that "succeeded":
  
https://github.com/let-me-illustrate/lmi/runs/1990831379?check_suite_focus=true