test_tkinter: use a context manager to close directly the pipe

Patch written by Nadeem Vawda
diff --git a/Lib/tkinter/test/test_tkinter/test_loadtk.py b/Lib/tkinter/test/test_tkinter/test_loadtk.py
index 8f1a085..bab7bcd 100644
--- a/Lib/tkinter/test/test_tkinter/test_loadtk.py
+++ b/Lib/tkinter/test/test_tkinter/test_loadtk.py
@@ -31,7 +31,8 @@
                 # doesn't actually carry through to the process level
                 # because they don't support unsetenv
                 # If that's the case, abort.
-                display = os.popen('echo $DISPLAY').read().strip()
+                with os.popen('echo $DISPLAY') as pipe:
+                    display = pipe.read().strip()
                 if display:
                     return
 
diff --git a/Misc/ACKS b/Misc/ACKS
index 6a3a25b..dccb779 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -866,6 +866,7 @@
 Atul Varma
 Dmitry Vasiliev
 Alexandre Vassalotti
+Nadeem Vawda
 Frank Vercruesse
 Mike Verdone
 Jaap Vermeulen