Switch monkeypatch fixture to yield syntax

AUTHORS

@@ -71,6 +71,7 @@ Janne Vanhala
 Jason R. Coombs
 Javier Domingo Cansino
 Javier Romero
+Jeff Widman
 John Towler
 Jon Sonesen
 Jordan Guymon

_pytest/monkeypatch.py

@@ -11,7 +11,7 @@ RE_IMPORT_ERROR_NAME = re.compile("^No module named (.*)$")
 
 
 @pytest.fixture
-def monkeypatch(request):
+def monkeypatch():
     """The returned ``monkeypatch`` fixture provides these
     helper methods to modify objects, dictionaries or os.environ::
 
@@ -30,8 +30,8 @@ def monkeypatch(request):
     will be raised if the set/deletion operation has no target.
     """
     mpatch = MonkeyPatch()
-    request.addfinalizer(mpatch.undo)
+    yield mpatch
-    return mpatch
+    mpatch.undo()
 
 
 def resolve(name):

testing/test_monkeypatch.py

@@ -7,17 +7,13 @@ from _pytest.monkeypatch import MonkeyPatch
 
 
 @pytest.fixture
-def mp(request):
+def mp():
     cwd = os.getcwd()
     sys_path = list(sys.path)
-
+    yield MonkeyPatch()
-    def cleanup():
     sys.path[:] = sys_path
     os.chdir(cwd)
 
-    request.addfinalizer(cleanup)
-    return MonkeyPatch()
-
 
 def test_setattr():
     class A:
@@ -329,5 +325,3 @@ def test_issue1338_name_resolving():
          monkeypatch.delattr('requests.sessions.Session.request')
     finally:
         monkeypatch.undo()
-
-