I ran pyflakes on Python 3.5. Attached patch fixes some undefined names warnings.

I don't know what to with these two warnings, they look to be false positive:

diff -r 72889bf8531d Lib/multiprocessing/spawn.py
--- a/Lib/multiprocessing/spawn.py      Tue Mar 18 13:21:29 2014 +0100
+++ b/Lib/multiprocessing/spawn.py      Wed Mar 19 11:49:24 2014 +0100
@@ -64,6 +64,7 @@ def freeze_support():
     Run code for process object if this in not the main process
     '''
     if is_forking(sys.argv):
+        # FIXME: main() is undefined
         main()
         sys.exit()
 
diff -r 72889bf8531d Lib/multiprocessing/synchronize.py
--- a/Lib/multiprocessing/synchronize.py        Tue Mar 18 13:21:29 2014 +0100
+++ b/Lib/multiprocessing/synchronize.py        Wed Mar 19 11:50:50 2014 +0100
@@ -51,7 +51,6 @@ class SemLock(object):
     _rand = tempfile._RandomNameSequence()
 
     def __init__(self, kind, value, maxvalue, *, ctx):
-        ctx = ctx or get_context()
         ctx = ctx.get_context()
         unlink_now = sys.platform == 'win32' or ctx._name == 'fork'
         for i in range(100):