Index: twisted/internet/fdesc.py
===================================================================
--- twisted/internet/fdesc.py	(revision 35633)
+++ twisted/internet/fdesc.py	(working copy)
@@ -16,8 +16,8 @@
 
 # twisted imports
 from twisted.internet.main import CONNECTION_LOST, CONNECTION_DONE
-from twisted.python.runtime import platformType
 
+
 def setNonBlocking(fd):
     """
     Make a file descriptor non-blocking.
@@ -84,7 +84,7 @@
     """
     try:
         output = os.read(fd, 8192)
-    except (OSError, IOError), ioe:
+    except (OSError, IOError) as ioe:
         if ioe.args[0] in (errno.EAGAIN, errno.EINTR):
             return
         else:
@@ -109,7 +109,7 @@
     """
     try:
         return os.write(fd, data)
-    except (OSError, IOError), io:
+    except (OSError, IOError) as io:
         if io.errno in (errno.EAGAIN, errno.EINTR):
             return 0
         return CONNECTION_LOST
Index: twisted/test/test_fdesc.py
===================================================================
--- twisted/test/test_fdesc.py	(revision 35633)
+++ twisted/test/test_fdesc.py	(working copy)
@@ -15,12 +15,43 @@
 else:
     from twisted.internet import fdesc
 
-from twisted.python.util import untilConcludes
+from twisted.python._utilpy3 import untilConcludes
 from twisted.trial import unittest
 
 
-class ReadWriteTestCase(unittest.TestCase):
+
+class NonBlockingTestCase(unittest.SynchronousTestCase):
     """
+    Tests for L{fdesc.setNonBlocking} and L{fdesc.setBlocking}.
+    """
+
+    def test_setNonBlocking(self):
+        """
+        L{fdesc.setNonBlocking} sets a file descriptor to non-blocking.
+        """
+        r, w = os.pipe()
+        self.addCleanup(os.close, r)
+        self.addCleanup(os.close, w)
+        self.assertFalse(fcntl.fcntl(r, fcntl.F_GETFL) & os.O_NONBLOCK)
+        fdesc.setNonBlocking(r)
+        self.assertTrue(fcntl.fcntl(r, fcntl.F_GETFL) & os.O_NONBLOCK)
+
+
+    def test_setBlocking(self):
+        """
+        L{fdesc.setBlocking} sets a file descriptor to blocking.
+        """
+        r, w = os.pipe()
+        self.addCleanup(os.close, r)
+        self.addCleanup(os.close, w)
+        fdesc.setNonBlocking(r)
+        fdesc.setBlocking(r)
+        self.assertFalse(fcntl.fcntl(r, fcntl.F_GETFL) & os.O_NONBLOCK)
+
+
+
+class ReadWriteTestCase(unittest.SynchronousTestCase):
+    """
     Tests for fdesc.readFromFD, fdesc.writeToFD.
     """
 
@@ -64,7 +95,7 @@
             if l:
                 return l[0]
             else:
-                return ""
+                return b""
         else:
             return res
 
@@ -74,11 +105,11 @@
         Test that the number of bytes L{fdesc.writeToFD} reports as written
         with its return value are seen by L{fdesc.readFromFD}.
         """
-        n = self.write("hello")
+        n = self.write(b"hello")
         self.failUnless(n > 0)
         s = self.read()
         self.assertEqual(len(s), n)
-        self.assertEqual("hello"[:n], s)
+        self.assertEqual(b"hello"[:n], s)
 
 
     def test_writeAndReadLarge(self):
@@ -86,7 +117,7 @@
         Similar to L{test_writeAndRead}, but use a much larger string to verify
         the behavior for that case.
         """
-        orig = "0123456879" * 10000
+        orig = b"0123456879" * 10000
         written = self.write(orig)
         self.failUnless(written > 0)
         result = []
@@ -97,7 +128,7 @@
             resultlength += len(result[-1])
             # Increment a counter to be sure we'll exit at some point
             i += 1
-        result = "".join(result)
+        result = b"".join(result)
         self.assertEqual(len(result), written)
         self.assertEqual(orig[:written], result)
 
@@ -128,7 +159,7 @@
         results in a connection lost indicator.
         """
         os.close(self.r)
-        self.assertEqual(self.write("s"), fdesc.CONNECTION_LOST)
+        self.assertEqual(self.write(b"s"), fdesc.CONNECTION_LOST)
 
 
     def test_readFromInvalid(self):
@@ -146,7 +177,7 @@
         closed results in a connection lost indicator.
         """
         os.close(self.w)
-        self.assertEqual(self.write("s"), fdesc.CONNECTION_LOST)
+        self.assertEqual(self.write(b"s"), fdesc.CONNECTION_LOST)
 
 
     def test_writeErrors(self):
@@ -160,7 +191,7 @@
             raise err
         os.write = eagainWrite
         try:
-            self.assertEqual(self.write("s"), 0)
+            self.assertEqual(self.write(b"s"), 0)
         finally:
             os.write = oldOsWrite
 
@@ -170,21 +201,21 @@
             raise err
         os.write = eintrWrite
         try:
-            self.assertEqual(self.write("s"), 0)
+            self.assertEqual(self.write(b"s"), 0)
         finally:
             os.write = oldOsWrite
 
 
 
-class CloseOnExecTests(unittest.TestCase):
+class CloseOnExecTests(unittest.SynchronousTestCase):
     """
     Tests for L{fdesc._setCloseOnExec} and L{fdesc._unsetCloseOnExec}.
     """
     program = '''
 import os, errno
 try:
-    os.write(%d, 'lul')
-except OSError, e:
+    os.write(%d, b'lul')
+except OSError as e:
     if e.errno == errno.EBADF:
         os._exit(0)
     os._exit(5)
@@ -215,7 +246,7 @@
         by a new process image created with one of the exec family of
         functions.
         """
-        fObj = file(self.mktemp(), 'w')
+        fObj = open(self.mktemp(), 'wb')
         fdesc._setCloseOnExec(fObj.fileno())
         status = self._execWithFileDescriptor(fObj)
         self.assertTrue(os.WIFEXITED(status))
@@ -227,7 +258,7 @@
         A file descriptor passed to L{fdesc._unsetCloseOnExec} is inherited by
         a new process image created with one of the exec family of functions.
         """
-        fObj = file(self.mktemp(), 'w')
+        fObj = open(self.mktemp(), 'wb')
         fdesc._setCloseOnExec(fObj.fileno())
         fdesc._unsetCloseOnExec(fObj.fileno())
         status = self._execWithFileDescriptor(fObj)
Index: admin/_twistedpython3.py
===================================================================
--- admin/_twistedpython3.py	(revision 35635)
+++ admin/_twistedpython3.py	(working copy)
@@ -22,6 +22,7 @@
     "twisted.internet",
     "twisted.internet.defer",
     "twisted.internet.interfaces",
+    "twisted.internet.fdesc",
     "twisted.internet.main",
     "twisted.internet.test",
     "twisted.internet.test.reactormixins",
@@ -67,6 +68,7 @@
     "twisted.test.test_context",
     "twisted.test.test_defer",
     "twisted.test.test_failure",
+    "twisted.test.test_fdesc",
     "twisted.test.test_log",
     "twisted.test.test_monkey",
     "twisted.test.test_paths",