Fix crash on shutdown

When the root directory being watched by inotify was deleted, watchdog
would crash with a KeyError when shutting down.

This commit stops watching the deleted directory for events once it's
been deleted, as well as adds a guard for the crash.

src/watchdog/observers/inotify_buffer.py

@@ -55,7 +55,8 @@ def run(self):
         IN_MOVE_TO event, remove the previous added matching IN_MOVE_FROM event
         and add them back to the queue as a tuple.
         """
-        while self.should_keep_running():
+        deleted_self = False
+        while self.should_keep_running() and not deleted_self:
             inotify_events = self._inotify.read_events()
             for inotify_event in inotify_events:
                 logger.debug("in-event %s", inotify_event)
@@ -74,3 +75,7 @@ def matching_from_event(event):
                 else:
                     self._queue.put(inotify_event)
 
+                if inotify_event.is_delete_self and \
+                        inotify_event.src_path == self._inotify.path:
+                    # Deleted the watched directory, stop watching for events
+                    deleted_self = True

src/watchdog/observers/inotify_c.py

@@ -257,8 +257,9 @@ def close(self):
         Closes the inotify instance and removes all associated watches.
         """
         with self._lock:
-            wd = self._wd_for_path[self._path]
-            inotify_rm_watch(self._inotify_fd, wd)
+            if self._path in self._wd_for_path:
+                wd = self._wd_for_path[self._path]
+                inotify_rm_watch(self._inotify_fd, wd)
             os.close(self._inotify_fd)
 
     def read_events(self, event_buffer_size=DEFAULT_EVENT_BUFFER_SIZE):

tests/test_inotify_buffer.py

@@ -19,7 +19,7 @@
 import random
 import pytest
 from tests import tmpdir, p  # pytest magic
-from .shell import mkdir, touch, mv
+from .shell import mkdir, touch, mv, rm
 from watchdog.observers.api import ObservedWatch
 from watchdog.utils import platform
 
@@ -104,6 +104,19 @@ def test_move_internal_batch(p):
     inotify.close()
 
 
+@pytest.mark.timeout(5)
+def test_delete_watched_directory(p):
+    mkdir(p('dir'))
+    inotify = InotifyBuffer(p('dir').encode())
+    rm(p('dir'), recursive=True)
+
+    # Wait for the event to be picked up
+    inotify.read_event()
+
+    # Ensure InotifyBuffer shuts down cleanly without raising an exception
+    inotify.close()
+
+
 def test_close_should_terminate_thread(p):
     inotify = InotifyBuffer(p('').encode(), recursive=True)
     assert inotify.is_alive()