monkey_patch_mimetools() now does nothing on py3

The mimetools module has been removed from Python 3: modify
monkey_patch_mimetools() to do nothing on Python 3.

Skip test_monkey_patch_mimetools() on Python 3.

Change-Id: I50f01ec159efedbb4df759ddd1e13928ac28fba6

swift/common/wsgi.py

@@ -22,7 +22,6 @@ import inspect
 import os
 import signal
 import time
-import mimetools
 from swift import gettext_ as _
 from textwrap import dedent
 
@@ -35,6 +34,8 @@ import six
 from six import BytesIO
 from six import StringIO
 from six.moves.urllib.parse import unquote
+if six.PY2:
+    import mimetools
 
 from swift.common import utils, constraints
 from swift.common.storage_policy import BindPortsCache
@@ -147,6 +148,9 @@ def monkey_patch_mimetools():
     mimetools.Message defaults content-type to "text/plain"
     This changes it to default to None, so we can detect missing headers.
     """
+    if six.PY3:
+        # The mimetools has been removed from Python 3
+        return
 
     orig_parsetype = mimetools.Message.parsetype
 

test/unit/common/test_wsgi.py

@@ -17,7 +17,6 @@
 
 import errno
 import logging
-import mimetools
 import socket
 import unittest
 import os
@@ -25,11 +24,15 @@ from textwrap import dedent
 from collections import defaultdict
 
 from eventlet import listen
+import six
 from six import BytesIO
 from six import StringIO
 from six.moves.urllib.parse import quote
+if six.PY2:
+    import mimetools
 
 import mock
+import nose
 
 import swift.common.middleware.catch_errors
 import swift.common.middleware.gatekeeper
@@ -65,12 +68,17 @@ class TestWSGI(unittest.TestCase):
 
     def setUp(self):
         utils.HASH_PATH_PREFIX = 'startcap'
-        self._orig_parsetype = mimetools.Message.parsetype
+        if six.PY2:
+            self._orig_parsetype = mimetools.Message.parsetype
 
     def tearDown(self):
-        mimetools.Message.parsetype = self._orig_parsetype
+        if six.PY2:
+            mimetools.Message.parsetype = self._orig_parsetype
 
     def test_monkey_patch_mimetools(self):
+        if six.PY3:
+            raise nose.SkipTest('test specific to Python 2')
+
         sio = StringIO('blah')
         self.assertEqual(mimetools.Message(sio).type, 'text/plain')
         sio = StringIO('blah')