[2.7] bpo-34275: Make IDLE calltips always visible on Mac. (GH-8639) (GH-8644)

Some MacOS-tk combinations need .update_idletasks().
The call is both unneeded and innocuous on Linux and Windows.
Patch by Kevin Walzer.

(cherry picked from commit 9beaef62)
Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

Lib/idlelib/CallTipWindow.py

@@ -72,6 +72,7 @@ class CallTip:
                            background="#ffffe0", relief=SOLID, borderwidth=1,
                            font = self.widget['font'])
         self.label.pack()
+        tw.update_idletasks()
         tw.lift()  # work around bug in Tk 8.5.18+ (issue #24570)
 
         self.checkhideid = self.widget.bind(CHECKHIDE_VIRTUAL_EVENT_NAME,

Misc/NEWS.d/next/IDLE/2018-08-02-22-16-42.bpo-34275.Iu0d7t.rst

+Make IDLE calltips always visible on Mac. Some MacOS-tk combinations need
+.update_idletasks(). Patch by Kevin Walzer.