contextlib: Use a list instead of deque for exit callbacks.

Since deque was removed from this repository the built-in one needs to be
used, and that doesn't have unbounded growth.  So use a list instead, which
is adequate becasue contextlib only needs append and pop, not double ended
behaviour (the previous pure-Python implementation of deque that was used
here anyway used a list as its storage container).

Also tweak the excessive-nesting test so it uses less memory and can run on
the unix port.

Signed-off-by: Damien George <damien@micropython.org>

python-stdlib/contextlib/contextlib.py

@@ -85,13 +85,13 @@ class ExitStack(object):
     """
 
     def __init__(self):
-        self._exit_callbacks = deque()
+        self._exit_callbacks = []
 
     def pop_all(self):
         """Preserve the context stack by transferring it to a new instance"""
         new_stack = type(self)()
         new_stack._exit_callbacks = self._exit_callbacks
-        self._exit_callbacks = deque()
+        self._exit_callbacks = []
         return new_stack
 
     def _push_cm_exit(self, cm, cm_exit):

python-stdlib/contextlib/manifest.py

@@ -1,4 +1,4 @@
-metadata(description="Port of contextlib for micropython", version="3.4.3")
+metadata(description="Port of contextlib for micropython", version="3.4.4")
 
 require("ucontextlib")
 require("collections")

python-stdlib/contextlib/tests.py

@@ -399,7 +399,7 @@ class TestExitStack(unittest.TestCase):
     def test_excessive_nesting(self):
         # The original implementation would die with RecursionError here
         with ExitStack() as stack:
-            for i in range(10000):
+            for i in range(5000):
                 stack.callback(int)
 
     def test_instance_bypass(self):