After switching from Python 3.7.0 to 3.7.1rc1 (macOS, 64-bit only downloaded from python.org), my rather big Tkinter application started to segfault whenever I close a system dialog (eg. the one created by askopenfilename or showerror) by keypress (eg. Escape or Enter). The crash does not happen when I close the dialog with mouse click.

The code that calls the dialog runs fine, and the crash seems to happen next time the control goes back to Tk mainloop. It looks like the keypress performed in the dialog somehow remains in Tk event queue.

Here is the system log for main thread, (more detailed information can be seen at https://bitbucket.org/plas/thonny/issues/545/quit):

Crashed Thread:        0  Dispatch queue: com.apple.main-thread

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000000000000
Exception Note:        EXC_CORPSE_NOTIFY

VM Regions Near 0:
--> 
    __TEXT                 000000010ab7e000-000000010ab7f000 [    4K] r-x/rwx SM=COW  /Users/USER/Desktop/Thonny.app/Contents/Frameworks/Python.framework/Versions/3.7/Resources/Python.app/Contents/MacOS/Python

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   libsystem_kernel.dylib          0x00007fff97e1a8ea __kill + 10
1   libsystem_platform.dylib        0x00007fff96dba52a _sigtramp + 26
2   ???                             000000000000000000 0 + 0
3   libtk8.6.dylib                  0x000000010b876e84 -[TKApplication(TKKeyEvent) tkProcessKeyEvent:] + 160
4   libtk8.6.dylib                  0x000000010b87d6d9 TkMacOSXEventsCheckProc + 360
5   libtcl8.6.dylib                 0x000000010b714d06 Tcl_DoOneEvent + 316
6   _tkinter.cpython-37m-darwin.so  0x000000010b64501d _tkinter_tkapp_mainloop + 269
7   org.python.python               0x000000010aba752e _PyMethodDef_RawFastCallKeywords + 430
8   org.python.python               0x000000010abad192 _PyMethodDescr_FastCallKeywords + 82
9   org.python.python               0x000000010ac6640c call_function + 780
10  org.python.python               0x000000010ac6339c _PyEval_EvalFrameDefault + 25164
11  org.python.python               0x000000010ac66f06 _PyEval_EvalCodeWithName + 2422
12  org.python.python               0x000000010aba6a61 _PyFunction_FastCallKeywords + 257
13  org.python.python               0x000000010ac663e2 call_function + 738
14  org.python.python               0x000000010ac633b6 _PyEval_EvalFrameDefault + 25190
15  org.python.python               0x000000010aba6ed0 function_code_fastcall + 128
16  org.python.python               0x000000010ac663e2 call_function + 738
17  org.python.python               0x000000010ac63457 _PyEval_EvalFrameDefault + 25351
18  org.python.python               0x000000010ac66f06 _PyEval_EvalCodeWithName + 2422
19  org.python.python               0x000000010ac5d074 PyEval_EvalCode + 100
20  org.python.python               0x000000010ac5a65d builtin_exec + 557
21  org.python.python               0x000000010aba752e _PyMethodDef_RawFastCallKeywords + 430
22  org.python.python               0x000000010aba6a9a _PyCFunction_FastCallKeywords + 42
23  org.python.python               0x000000010ac663d4 call_function + 724
24  org.python.python               0x000000010ac63457 _PyEval_EvalFrameDefault + 25351
25  org.python.python               0x000000010ac66f06 _PyEval_EvalCodeWithName + 2422
26  org.python.python               0x000000010aba6a61 _PyFunction_FastCallKeywords + 257
27  org.python.python               0x000000010ac663e2 call_function + 738
28  org.python.python               0x000000010ac63457 _PyEval_EvalFrameDefault + 25351
29  org.python.python               0x000000010ac66f06 _PyEval_EvalCodeWithName + 2422
30  org.python.python               0x000000010aba663b _PyFunction_FastCallDict + 523
31  org.python.python               0x000000010acb8743 pymain_run_module + 147
32  org.python.python               0x000000010acb7b47 pymain_main + 5303
33  org.python.python               0x000000010acb868a _Py_UnixMain + 58
34  libdyld.dylib                   0x00007fff921c35ad start + 1