faulthandler module caught a hang just now:

    Timeout (0:01:00)!
    Thread 0x00000eb0 (most recent call first):
      File "D:\git\tz2txt\tz2txt\gui.py", line 262 in delfile
      File "C:\Python35\lib\tkinter\__init__.py", line 1549 in __call__
      File "C:\Python35\lib\tkinter\__init__.py", line 1131 in mainloop
      File "D:\git\tz2txt\tz2txt\gui.py", line 328 in main
      File "D:\git\tz2txt\tz2txt\gui.py", line 331 in <module>
  
 Here is the full delfile function:
  
      def delfile(self):
        try:
            output = self.output.get().strip()
            os.remove(output)
        except:
            pass
        else:
            print('已删除输出文件')    # <- line 262
        
        try:
            os.remove(discard_fn)
        except:
            pass
        else:
            print('已删除丢弃文件')
        
        self.url.set(url_use)

~~~~~~~~~~~~~~~~~~~~~~~~~~
Some supplemental information:

There was a time point, *maybe* it's Windows10 Threshold2 (12/Nov/2015), before that time no hang at all.
After that time, the hangs were quite often.
Some months later, the frequency had declined a lot, but still hang occasionally.