use xfail_strict and adapt affected tests

CHANGELOG

@@ -11,7 +11,6 @@
 	where they are not used.
 - #326: Fix OSError 'Not a directory' when creating env on Jython 2.7.0.
         Thanks Nick Douma (@LordGaav).
-- #585: Add documentation for constraints.txt
 
 2.7.0
 -----

tests/test_config.py

@@ -1108,8 +1108,7 @@ def test_substitution_notfound_issue515(tmpdir, newconfig):
             ['python', '-c', 'print("Hello, world!")'],
         ]
 
-    @pytest.mark.xfail(raises=AssertionError, reason="issue #301")
-    def test_substitution_nested_env_defaults_issue301(tmpdir, newconfig, monkeypatch):
+    def test_substitution_nested_env_defaults(tmpdir, newconfig, monkeypatch):
         monkeypatch.setenv("IGNORE_STATIC_DEFAULT", "env")
         monkeypatch.setenv("IGNORE_DYNAMIC_DEFAULT", "env")
         config = newconfig("""
@@ -1684,9 +1683,6 @@ def test_passing_empty_string(self, tmpdir, newconfig):
         args = ['--hashseed', '']
         self._check_testenv(newconfig, '', args=args)
 
-    @pytest.mark.xfail(sys.version_info >= (3, 2),
-                       reason="at least Debian python 3.2/3.3 have a bug: "
-                              "http://bugs.python.org/issue11884")
     def test_passing_no_argument(self, tmpdir, newconfig):
         """Test that passing no arguments to --hashseed is not allowed."""
         args = ['--hashseed']
@@ -2190,7 +2186,9 @@ def test_showconfig_with_force_dep_version(self, cmd, initproj):
             r'*deps*dep1, dep2==5.0*',
         ])
 
-    @pytest.mark.xfail(reason='Upstream bug. See #203')
+    @pytest.mark.xfail(
+        "'pypy' not in sys.executable",
+        reason='Upstream bug. See #203')
     def test_colon_symbol_in_directory_name(self, cmd, initproj):
         initproj('colon:_symbol_in_dir_name', filedefs={
             'tox.ini': '''

tests/test_z_cmdline.py

@@ -782,7 +782,6 @@ def test_installpkg(tmpdir, newconfig):
     assert sdist_path == p
 
 
-@pytest.mark.xfail("sys.platform == 'win32'", reason="test needs better impl")
 def test_envsitepackagesdir(cmd, initproj):
     initproj("pkg512-0.0.5", filedefs={
         'tox.ini': """
@@ -797,7 +796,6 @@ def test_envsitepackagesdir(cmd, initproj):
     """)
 
 
-@pytest.mark.xfail("sys.platform == 'win32'", reason="test needs better impl")
 def test_envsitepackagesdir_skip_missing_issue280(cmd, initproj):
     initproj("pkg513-0.0.5", filedefs={
         'tox.ini': """

tox.ini

@@ -60,3 +60,4 @@ pep8maxlinelength = 99
 # E731 - do not assign a lambda expression, use a def
 pep8ignore = *.py W503 E402 E731
 flakes-ignore = ImportStarUsage
+xfail_strict = True