Back out 7e9605697dfc, 2e3c31ab586a, 759b2cecc289.

These added a path attribute to pathlib.Path objects, and docs.
Instead, we're going to use PEP 519.

(Starting in the 3.4 branch and merging forward from there since that's what I did originally.)

Lib/pathlib.py

@@ -648,13 +648,6 @@ class PurePath(object):
                                                   self._parts) or '.'
             return self._str
 
-    @property
-    def path(self):
-        try:
-            return self._str
-        except AttributeError:
-            return str(self)
-
     def as_posix(self):
         """Return the string representation of the path with forward (/)
         slashes."""