gtk3: remove test for the DISPLAY variable

As the code does not depend on this variable any more,
testing for it does not make sense.

There might be more logic to remove, since
4142aee
introduced it.

src/twisted/internet/test/test_gireactor.py

@@ -6,7 +6,6 @@
 """
 
 
-import os
 import sys
 from unittest import skipIf
 try:
@@ -27,11 +26,9 @@
         gtk3reactor = _gtk3reactor
         from gi.repository import Gtk
 
-from twisted.python.runtime import platform
 from twisted.internet.error import ReactorAlreadyRunning
 from twisted.trial.unittest import TestCase, SkipTest
 from twisted.internet.test.reactormixins import ReactorBuilder
-from twisted.test.test_twisted import SetAsideModule
 
 # Skip all tests if gi is unavailable:
 if gireactor is None:
@@ -187,29 +184,3 @@ def test_compatibilityLayer(self):
             raise SkipTest("This version of gi doesn't include pygtkcompat.")
         import gobject
         self.assertTrue(gobject.__name__.startswith("gi."))
-
-
-
-class Gtk3ReactorTests(TestCase):
-    """
-    Tests for L{gtk3reactor}.
-    """
-
-    @skipIf(platform.getType() != "posix" or platform.isMacOSX(),
-            "This test is only relevant when using X11")
-    def test_requiresDISPLAY(self):
-        """
-        On X11, L{gtk3reactor} is unimportable if the C{DISPLAY} environment
-        variable is not set.
-        """
-        display = os.environ.get("DISPLAY", None)
-        if display is not None:
-            self.addCleanup(os.environ.__setitem__, "DISPLAY", display)
-            del os.environ["DISPLAY"]
-        with SetAsideModule("twisted.internet.gtk3reactor"):
-            exc = self.assertRaises(ImportError,
-                                    __import__, "twisted.internet.gtk3reactor")
-            self.assertEqual(
-                exc.args[0],
-                "Gtk3 requires X11, and no DISPLAY environment "
-                "variable is set")