The test for the condition was added to solve the problem reported in Issue8716.  The Tk crash for test_ttk_guionly reported there still occurs on a current 10.8 system with the Apple-supplied Cocoa Tk under the same conditions, that is, when running the tests from a process without a window manager connection, like an ssh or buildbot process where the user is not also currently logged in as the main "GUI user".  And the skip test code in question does prevent that crash.  The skip test also works correctly when using a 64-bit framework Python build (./configure --enable-framework), i.e. it does not skip the tests in a normal terminal session.  A side effect of a framework build is that the Python interpreter runs within an OS X app bundle, which gives it magic GUI powers.

But if run from a non-framework (standard unix) build, the tests are skipped with a "cannot run without OS X gui process" skip although stubbing out the check, as your patch does, shows that test_tk and test_ttk_guionly appear to run without error.  So it seems that the skip test is too restrictive but it shouldn't be unilaterally deleted.