Make test.test_support.EnvironmentVarGuard behave like a dictionary.

All changes are mirrored to the underlying os.environ dict, but rolled back
on exit from the with block.

1 files changed, 11 insertions, 14 deletions

diff --git a/Lib/test/test_tcl.py b/Lib/test/test_tcl.py
index 0b05c54fe3..5d16968fdd 100644
--- a/Lib/test/test_tcl.py
+++ b/Lib/test/test_tcl.py
@@ -144,23 +144,20 @@ class TclTest(unittest.TestCase):
         import sys
         if sys.platform.startswith(('win', 'darwin', 'cygwin')):
             return  # no failure possible on windows?
-        if 'DISPLAY' in os.environ:
-            old_display = os.environ['DISPLAY']
-            del os.environ['DISPLAY']
-            # on some platforms, deleting environment variables
-            # 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()
-            if display:
-                return
-        try:
+        with test_support.EnvironmentVarGuard() as env:
+            if 'DISPLAY' in os.environ:
+                del env['DISPLAY']
+                # on some platforms, deleting environment variables
+                # 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()
+                if display:
+                    return
+
             tcl = Tcl()
             self.assertRaises(TclError, tcl.winfo_geometry)
             self.assertRaises(TclError, tcl.loadtk)
-        finally:
-            if old_display is not None:
-                os.environ['DISPLAY'] = old_display
 
 def test_main():
     test_support.run_unittest(TclTest, TkinterTest)