Ensure ObservedWatch.path is a string (fix gorakhargosh#651)

src/watchdog/observers/api.py

@@ -17,6 +17,7 @@
 # limitations under the License.
 
 from __future__ import with_statement
+import os
 import threading
 from watchdog.utils import BaseThread
 from watchdog.utils.compat import queue
@@ -40,13 +41,16 @@ class ObservedWatch(object):
     """An scheduled watch.
 
     :param path:
-        Path string.
+        Path string.  # TODO: this comment is not true
     :param recursive:
         ``True`` if watch is recursive; ``False`` otherwise.
     """
 
     def __init__(self, path, recursive):
-        self._path = path
+        if isinstance(path, getattr(os, 'PathLike', ())):
+            self._path = os.fspath(path)
+        else:
+            self._path = path
         self._is_recursive = recursive
 
     @property