Add a as_uri() method as suggested by Charles-François, to return a file URI.

pep-0428.txt

@@ -341,6 +341,15 @@ call ``bytes()`` on it, or use the ``as_bytes()`` method::
     >>> bytes(p)
     b'/home/antoine/pathlib/setup.py'
 
+To represent the path as a ``file`` URI, call the ``as_uri()`` method::
+
+    >>> p = PurePosixPath('/etc/passwd')
+    >>> p.as_uri()
+    'file:///etc/passwd'
+    >>> p = PureNTPath('c:/Windows')
+    >>> p.as_uri()
+    'file:///c:/Windows'
+
 
 Properties
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