bpo-34711: Return HTTPStatus.NOT_FOUND if path.endswith('/') and not a directory (GH-9687)

AIX allows a trailing slash on local file system paths, which isn't what we want
in http.server. Accordingly, check explicitly for this case in the server code,
rather than relying on the OS raising an exception.

Patch by Michael Felt.

Lib/http/server.py

@@ -692,6 +692,14 @@ class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
             else:
                 return self.list_directory(path)
         ctype = self.guess_type(path)
+        # check for trailing "/" which should return 404. See Issue17324
+        # The test for this was added in test_httpserver.py
+        # However, some OS platforms accept a trailingSlash as a filename
+        # See discussion on python-dev and Issue34711 regarding
+        # parseing and rejection of filenames with a trailing slash
+        if path.endswith("/"):
+            self.send_error(HTTPStatus.NOT_FOUND, "File not found")
+            return None
         try:
             f = open(path, 'rb')
         except OSError:

Misc/NEWS.d/next/Library/2018-10-03-09-25-02.bpo-34711.HeOmKR.rst

@@ -0,0 +1,3 @@
+http.server ensures it reports HTTPStatus.NOT_FOUND when the local path ends with "/"
+and is not a directory, even if the underlying OS (e.g. AIX) accepts such paths as a
+valid file reference. Patch by Michael Felt.