I am getting exceptions from /usr/lib/python3.5/weakref.py, is it an issue?

When starting or stopping REVEN’s Project Manager, the following exception is displayed in the terminal, one or more times:

Exception ignored in: <function WeakValueDictionary.__init__.<locals>.remove at 0x7f2bc24c40d0>
Traceback (most recent call last):
 File "/usr/lib/python3.5/weakref.py", line 117, in remove
TypeError: 'NoneType' object is not callable

This behavior is not an issue in REVEN. It is a well known exception (Python issue 29519) that affects the version of Python used in Debian 9 Stretch. When encountered, it means that this particular Python process has leaked some memory, but this won’t impact the successful completion of the operations.

A patch is available for /usr/lib/python3.5/weakref.py. Since it is a system file, it is not applied by REVEN.

diff --git a/usr/lib/python3.5/weakref.py b/usr/lib/python3.5/weakref.py
index c66943f02e24..3e1fb8158069 100644
--- a/usr/lib/python3.5/weakref.py
+++ b/usr/lib/python3.5/weakref.py
@@ -53,7 +53,7 @@ def __init__(*args, **kw):
         args = args[1:]
         if len(args) > 1:
             raise TypeError('expected at most 1 arguments, got %d' % len(args))
-        def remove(wr, selfref=ref(self)):
+        def remove(wr, selfref=ref(self), _atomic_removal=_remove_dead_weakref):
             self = selfref()
             if self is not None:
                 if self._iterating:
@@ -61,7 +61,7 @@ def remove(wr, selfref=ref(self)):
                 else:
                     # Atomic removal is necessary since this function
                     # can be called asynchronously by the GC
-                    _remove_dead_weakref(self.data, wr.key)
+                    _atomic_removal(self.data, wr.key)
         self._remove = remove
         # A list of keys to be removed
         self._pending_removals = []