title: get rid of blank space around widgets in tkinter
body: <p>I put widgets on a window with <code>.grid</code> and noticed that the widgets have space around them. I fixed that on canvas widget with <code>highlightthickness</code> but this doesn't work with button widgets. It doesn't look cool when you have grey window background and there's white space around buttons.
  P.S. I use python3 on macos Sierra</p>
  
  <pre><code>root = Tk()
  root.configure(bg='grey')
  
  w = Canvas(root, width=150, height=150, highlightthickness=0)
  w.grid(row=1, column=1, sticky="nsew")
  
  clear_btn = Button(text="Clear", width=15, command=lambda: w.delete("all"))
  clear_btn.grid(row=2, column=1)
  
  root.mainloop()
  </code></pre>
  
  <p>P.S. <a href="https://stackoverflow.com/questions/27084321/tkinter-leaving-borders-around-widgets">TKinter leaving borders around widgets</a> that's what it looks like. The guy was advised to use <code>highlightbackground</code>, but when I screenshot widgets, I still have that blank space around the widget.</p>