"py-bt-full" and add a smarter "py-bt" command printing a classic Python
traceback.

a smarter "py-bt" command printing a classic Python traceback.

on a file opened in read+write mode (namely: reading, seeking a bit forward,
writing, then seeking before the previous write but still within buffered
data, and writing again).

on a file opened in read+write mode (namely: reading, seeking a bit forward,
writing, then seeking before the previous write but still within buffered
data, and writing again).

on a file opened in read+write mode (namely: reading, seeking a bit forward,
writing, then seeking before the previous write but still within buffered
data, and writing again).

Issue #11896: Save on Close failed despite selecting "Yes" in dialog.

_tkinter.c is returning <class '_tkinter.Tcl_Obj'> sometimes.  Don't use
tkinter.messagebox.Message - use the helper functions which convert to str.

  wait for the process to end when exiting the context to avoid unintentionally
  leaving zombie processes around.