Use concurrent.futures classes and constants when the module is available

3 files changed, 28 insertions, 15 deletions

diff --git a/TODO b/TODO
index 6d38e74..50b7844 100644
--- a/TODO
+++ b/TODO
@@ -5,7 +5,6 @@
   - test_queues.py
   - test_tasks.py
 
-* Use backport of concurrent.futures
 * unix_events, RuntimeError on signal.signal:
   test_unix_events.SelectorEventLoopTests.test_add_signal_handler_install_error
 * Fix all FIXME in the code
diff --git a/asyncio/futures.py b/asyncio/futures.py
index 27a0feb..28f7866 100644
--- a/asyncio/futures.py
+++ b/asyncio/futures.py
@@ -24,17 +24,24 @@ _FINISHED = 'FINISHED'
 
 _PY34 = sys.version_info >= (3, 4)
 
-class Error(Exception):
-    """Base class for all future-related exceptions."""
-    pass
-
-class CancelledError(Error):
-    """The Future was cancelled."""
-    pass
-
-class TimeoutError(Error):
-    """The operation exceeded the given deadline."""
-    pass
+try:
+    import concurrent.futures._base
+except ImportError:
+    class Error(Exception):
+        """Base class for all future-related exceptions."""
+        pass
+
+    class CancelledError(Error):
+        """The Future was cancelled."""
+        pass
+
+    class TimeoutError(Error):
+        """The operation exceeded the given deadline."""
+        pass
+else:
+    Error = concurrent.futures._base.Error
+    CancelledError = concurrent.futures.CancelledError
+    TimeoutError = concurrent.futures.TimeoutError
 
 STACK_DEBUG = logging.DEBUG - 1  # heavy-duty debugging
 
diff --git a/asyncio/tasks.py b/asyncio/tasks.py
index 596b71f..46a9346 100644
--- a/asyncio/tasks.py
+++ b/asyncio/tasks.py
@@ -269,9 +269,16 @@ class Task(futures.Future):
 
 # wait() and as_completed() similar to those in PEP 3148.
 
-FIRST_COMPLETED = 'FIRST_COMPLETED'
-FIRST_EXCEPTION = 'FIRST_EXCEPTION'
-ALL_COMPLETED = 'ALL_COMPLETED'
+try:
+    import concurrent.futures
+except ImportError:
+    FIRST_COMPLETED = 'FIRST_COMPLETED'
+    FIRST_EXCEPTION = 'FIRST_EXCEPTION'
+    ALL_COMPLETED = 'ALL_COMPLETED'
+else:
+    FIRST_COMPLETED = concurrent.futures.FIRST_COMPLETED
+    FIRST_EXCEPTION = concurrent.futures.FIRST_EXCEPTION
+    ALL_COMPLETED = concurrent.futures.ALL_COMPLETED
 
 
 @coroutine