title: Why does <<ListboxSelect>> binding in Python's Tkinter trigger spuriously when double clicking an Entry widget?
body: <p>As part of a larger bock of code, I discovered an oddity with tkinter listbox bindings. The below code gives a breakdown of the issue. When binding a listbox with 'listboxselected', selecting an item within that listbox, then double left clicking on the Entry, the listboxselected event is triggered once. </p>
  
  <p>I have tested this in python 3.3.2, 3.6.3 and 3.7.1. The error only occurs in the two latter versions. I have checked the doc's and cant find any updates to cause this issue. Does anyone have any idea to why this behaviour may be occurring?</p>
  
  <pre><code>from tkinter import Tk, Listbox, Entry, Button
  from functools import partial
  
  root = Tk()
  
  myList = Listbox(root)
  myList.insert("end", "spam", "eggs", "chips")
  myList.pack()
  myList.bind("&lt;&lt;ListboxSelect&gt;&gt;", partial(print))
  
  myEntry = Entry(root)
  myEntry.pack()
  </code></pre>