asyncio: Tulip issue 173: Enhance repr(Handle) and repr(Task)

repr(Handle) is shorter for function: "foo" instead of "<function foo at
0x...>". It now also includes the source of the callback, filename and line
number where it was defined, if available.

repr(Task) now also includes the current position in the code, filename and
line number, if available. If the coroutine (generator) is done, the line
number is omitted and "done" is added.

Lib/test/test_asyncio/test_tasks.py

@@ -116,21 +116,30 @@ class TaskTests(unittest.TestCase):
             yield from []
             return 'abc'
 
+        filename, lineno = test_utils.get_function_source(notmuch)
+        src = "%s:%s" % (filename, lineno)
+
         t = asyncio.Task(notmuch(), loop=self.loop)
         t.add_done_callback(Dummy())
-        self.assertEqual(repr(t), 'Task(<notmuch>)<PENDING, [Dummy()]>')
+        self.assertEqual(repr(t),
+                         'Task(<notmuch at %s>)<PENDING, [Dummy()]>' % src)
+
         t.cancel()  # Does not take immediate effect!
-        self.assertEqual(repr(t), 'Task(<notmuch>)<CANCELLING, [Dummy()]>')
+        self.assertEqual(repr(t),
+                         'Task(<notmuch at %s>)<CANCELLING, [Dummy()]>' % src)
         self.assertRaises(asyncio.CancelledError,
                           self.loop.run_until_complete, t)
-        self.assertEqual(repr(t), 'Task(<notmuch>)<CANCELLED>')
+        self.assertEqual(repr(t),
+                         'Task(<notmuch done at %s>)<CANCELLED>' % filename)
+
         t = asyncio.Task(notmuch(), loop=self.loop)
         self.loop.run_until_complete(t)
-        self.assertEqual(repr(t), "Task(<notmuch>)<result='abc'>")
+        self.assertEqual(repr(t),
+                         "Task(<notmuch done at %s>)<result='abc'>" % filename)
 
     def test_task_repr_custom(self):
         @asyncio.coroutine
-        def coro():
+        def notmuch():
             pass
 
         class T(asyncio.Future):
@@ -141,10 +150,14 @@ class TaskTests(unittest.TestCase):
             def __repr__(self):
                 return super().__repr__()
 
-        gen = coro()
+        gen = notmuch()
         t = MyTask(gen, loop=self.loop)
-        self.assertEqual(repr(t), 'T[](<coro>)')
-        gen.close()
+        filename = gen.gi_code.co_filename
+        lineno = gen.gi_frame.f_lineno
+        # FIXME: check for the name "coro" instead of "notmuch" because
+        # @asyncio.coroutine drops the name of the wrapped function:
+        # http://bugs.python.org/issue21205
+        self.assertEqual(repr(t), 'T[](<coro at %s:%s>)' % (filename, lineno))
 
     def test_task_basics(self):
         @asyncio.coroutine