diff --git a/Lib/test/test_idle.py b/Lib/test/test_idle.py
index 495b416..66dd8af 100644
--- a/Lib/test/test_idle.py
+++ b/Lib/test/test_idle.py
@@ -1,24 +1,12 @@
 import unittest
 from test import test_support as support
-from test.test_support import import_module, use_resources
+from test.test_support import import_module
 
 # Skip test if _thread or _tkinter wasn't built or idlelib was deleted.
 import_module('threading')  # imported by idlelib.PyShell, imports _thread
 tk = import_module('Tkinter')  # imports _tkinter
 idletest = import_module('idlelib.idle_test')
 
-# If buildbot improperly sets gui resource (#18365, #18441), remove it
-# so requires('gui') tests are skipped while non-gui tests still run.
-# If there is a problem with Macs, see #18441, msg 193805
-if use_resources and 'gui' in use_resources:
-    try:
-        root = tk.Tk()
-        root.destroy()
-        del root
-    except tk.TclError:
-        while 'gui' in use_resources:
-            use_resources.remove('gui')
-
 # Without test_main present, regrtest.runtest_inner (line1219) calls
 # unittest.TestLoader().loadTestsFromModule(this_module) which calls
 # load_tests() if it finds it. (Unittest.main does the same.)
diff --git a/Lib/test/test_support.py b/Lib/test/test_support.py
index 44b4224..31b3119 100644
--- a/Lib/test/test_support.py
+++ b/Lib/test/test_support.py
@@ -270,12 +270,16 @@
         # is exited) but there is a .pyo file.
         unlink(os.path.join(dirname, modname + os.extsep + 'pyo'))
 
-# On some platforms, should not run gui test even if it is allowed
-# in `use_resources'.
-if sys.platform.startswith('win'):
-    import ctypes
-    import ctypes.wintypes
-    def _is_gui_available():
+# Check whether a gui is actually available
+def _is_gui_available():
+    if hasattr(_is_gui_available, 'result'):
+        return _is_gui_available.result
+    reason = None
+    if sys.platform.startswith('win'):
+        # if Python is running as a service (such as the buildbot service),
+        # gui interaction may be disallowed
+        import ctypes
+        import ctypes.wintypes
         UOI_FLAGS = 1
         WSF_VISIBLE = 0x0001
         class USEROBJECTFLAGS(ctypes.Structure):
@@ -295,10 +299,49 @@
             ctypes.byref(needed))
         if not res:
             raise ctypes.WinError()
-        return bool(uof.dwFlags & WSF_VISIBLE)
-else:
-    def _is_gui_available():
-        return True
+        if not bool(uof.dwFlags & WSF_VISIBLE):
+            reason = "gui not available (WSF_VISIBLE flag not set)"
+    elif sys.platform == 'darwin':
+        # The Aqua Tk implementations on OS X can abort the process if
+        # being called in an environment where a window server connection
+        # cannot be made, for instance when invoked by a buildbot or ssh
+        # process not running under the same user id as the current console
+        # user.  To avoid that, raise an exception if the window manager
+        # connection is not available.
+        from ctypes import cdll, c_int, pointer, Structure
+        from ctypes.util import find_library
+
+        app_services = cdll.LoadLibrary(find_library("ApplicationServices"))
+
+        if app_services.CGMainDisplayID() == 0:
+            reason = "gui tests cannot run without OS X window manager"
+        else:
+            class ProcessSerialNumber(Structure):
+                _fields_ = [("highLongOfPSN", c_int),
+                            ("lowLongOfPSN", c_int)]
+            psn = ProcessSerialNumber()
+            psn_p = pointer(psn)
+            if (  (app_services.GetCurrentProcess(psn_p) < 0) or
+                  (app_services.SetFrontProcess(psn_p) < 0) ):
+                reason = "cannot run without OS X gui process"
+
+    # check on every platform whether tkinter can actually do anything
+    if not reason:
+        try:
+            from Tkinter import Tk
+            root = Tk()
+            root.destroy()
+        except Exception as e:
+            err_string = str(e)
+            if len(err_string) > 50:
+                err_string = err_string[:50] + ' [...]'
+            reason = 'Tk unavailable due to {}: {}'.format(type(e).__name__,
+                                                           err_string)
+
+    _is_gui_available.reason = reason
+    _is_gui_available.result = not reason
+
+    return _is_gui_available.result
 
 def is_resource_enabled(resource):
     """Test whether a resource is enabled.  Known resources are set by
@@ -311,7 +354,7 @@
     If the caller's module is __main__ then automatically return True.  The
     possibility of False being returned occurs when regrtest.py is executing."""
     if resource == 'gui' and not _is_gui_available():
-        raise unittest.SkipTest("Cannot use the 'gui' resource")
+        raise ResourceDenied(_is_gui_available.reason)
     # see if the caller's module is __main__ - if so, treat as if
     # the resource was set
     if sys._getframe(1).f_globals.get("__name__") == "__main__":
@@ -1213,7 +1256,7 @@
 
 def requires_resource(resource):
     if resource == 'gui' and not _is_gui_available():
-        return unittest.skip("resource 'gui' is not available")
+        return unittest.skip(_is_gui_available.reason)
     if is_resource_enabled(resource):
         return _id
     else:
diff --git a/Lib/test/test_tk.py b/Lib/test/test_tk.py
index 8625db2..56eef47 100644
--- a/Lib/test/test_tk.py
+++ b/Lib/test/test_tk.py
@@ -1,8 +1,9 @@
 import os
 from test import test_support
 
-# Skip test if _tkinter wasn't built.
+# Skip test if _tkinter wasn't built or gui resource is not available.
 test_support.import_module('_tkinter')
+test_support.requires('gui')
 
 this_dir = os.path.dirname(os.path.abspath(__file__))
 lib_tk_test = os.path.abspath(os.path.join(this_dir, os.path.pardir,
@@ -11,9 +12,6 @@
 with test_support.DirsOnSysPath(lib_tk_test):
     import runtktests
 
-# Skip test if tk cannot be initialized.
-runtktests.check_tk_availability()
-
 def test_main(enable_gui=False):
     if enable_gui:
         if test_support.use_resources is None:
diff --git a/Lib/test/test_ttk_guionly.py b/Lib/test/test_ttk_guionly.py
index e0368be..47ddefb 100644
--- a/Lib/test/test_ttk_guionly.py
+++ b/Lib/test/test_ttk_guionly.py
@@ -2,8 +2,9 @@
 import unittest
 from test import test_support
 
-# Skip this test if _tkinter wasn't built.
+# Skip this test if _tkinter wasn't built or gui resource is not available.
 test_support.import_module('_tkinter')
+test_support.requires('gui')
 
 this_dir = os.path.dirname(os.path.abspath(__file__))
 lib_tk_test = os.path.abspath(os.path.join(this_dir, os.path.pardir,
@@ -12,9 +13,6 @@
 with test_support.DirsOnSysPath(lib_tk_test):
     import runtktests
 
-# Skip test if tk cannot be initialized.
-runtktests.check_tk_availability()
-
 import ttk
 from _tkinter import TclError