Attempt to mitigate lookups on unexistant Watch objects triggered

in presently not well understood contexts. These faulty? events
are currently skipped but should be dumped into debug traces.

python2/pyinotify.py

@@ -730,6 +730,13 @@ def process_default(self, raw_event, to_append=None):
         IN_OPEN, IN_DELETE, IN_DELETE_SELF, IN_UNMOUNT.
         """
         watch_ = self._watch_manager.get_watch(raw_event.wd)
+        if watch_ is None:
+            # Not really sure how we ended up here, nor how we should
+            # handle these types of events and if it is appropriate to
+            # completly skip them or not (like we are doing here).
+            log.debug("Unable to retrieve Watch object associated to event %s",
+                      repr(raw_event))
+            return
         if raw_event.mask & (IN_DELETE_SELF | IN_MOVE_SELF):
             # Unfornulately this information is not provided by the kernel
             dir_ = watch_.dir
@@ -1122,6 +1129,8 @@ def process_events(self):
             raw_event = self._eventq.popleft()  # pop next event
             watch_ = self._watch_manager.get_watch(raw_event.wd)
             revent = self._sys_proc_fun(raw_event)  # system processings
+            if revent is None:
+                continue
             if watch_ and watch_.proc_fun:
                 watch_.proc_fun(revent)  # user processings
             else:

python3/pyinotify.py

@@ -694,6 +694,13 @@ def process_default(self, raw_event, to_append=None):
         IN_OPEN, IN_DELETE, IN_DELETE_SELF, IN_UNMOUNT.
         """
         watch_ = self._watch_manager.get_watch(raw_event.wd)
+        if watch_ is None:
+            # Not really sure how we ended up here, nor how we should
+            # handle these types of events and if it is appropriate to
+            # completly skip them or not (like we are doing here).
+            log.debug("Unable to retrieve Watch object associated to event %s",
+                      repr(raw_event))
+            return
         if raw_event.mask & (IN_DELETE_SELF | IN_MOVE_SELF):
             # Unfornulately this information is not provided by the kernel
             dir_ = watch_.dir
@@ -1085,6 +1092,8 @@ def process_events(self):
             raw_event = self._eventq.popleft()  # pop next event
             watch_ = self._watch_manager.get_watch(raw_event.wd)
             revent = self._sys_proc_fun(raw_event)  # system processings
+            if revent is None:
+                continue
             if watch_ and watch_.proc_fun:
                 watch_.proc_fun(revent)  # user processings
             else: