Checking for tk availability before continuing (basically the same that is done in test_ttk_guionly)

Lib/test/test_tk.py

@@ -1,8 +1,14 @@
 import os
 import sys
-from _tkinter import TclError
+import Tkinter
 from test import test_support
 
+try:
+    Tkinter.Button()
+except Tkinter.TclError, msg:
+    # assuming tk is not available
+    raise test_support.TestSkipped("tk not available: %s" % msg)
+
 this_dir = os.path.dirname(os.path.abspath(__file__))
 lib_tk_test = os.path.abspath(os.path.join(this_dir, os.path.pardir,
     'lib-tk', 'test'))