Revert "Migrate as much as possible to pip and requirements.txt"

This reverts commit 982594a4a5.

lib/concurrent/futures/__init__.py

@@ -0,0 +1,23 @@
+# Copyright 2009 Brian Quinlan. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""Execute computations asynchronously using threads or processes."""
+
+__author__ = 'Brian Quinlan (brian@sweetapp.com)'
+
+from concurrent.futures._base import (FIRST_COMPLETED,
+                                      FIRST_EXCEPTION,
+                                      ALL_COMPLETED,
+                                      CancelledError,
+                                      TimeoutError,
+                                      Future,
+                                      Executor,
+                                      wait,
+                                      as_completed)
+from concurrent.futures.thread import ThreadPoolExecutor
+
+# Jython doesn't have multiprocessing
+try:
+    from concurrent.futures.process import ProcessPoolExecutor
+except ImportError:
+    pass