#5551: symbolic links never can be mount points. Fixes the fix for #1713.

Lib/posixpath.py

@@ -200,6 +200,9 @@ def samestat(s1, s2):
 
 def ismount(path):
     """Test whether a path is a mount point"""
+    if islink(path):
+        # A symlink can never be a mount point
+        return False
     try:
         s1 = os.lstat(path)
         if isinstance(path, bytes):

Misc/NEWS

@@ -29,6 +29,9 @@ Extensions
 Library
 -------
 
+- Issue #1713: Fix os.path.ismount(), which returned true for symbolic links
+  across devices.
+
 - Issue #8826: Properly load old-style "expires" attribute in http.cookies.
 
 - Issue #1690103: Fix initial namespace for code run with trace.main().