bpo-33721: Make some os.path functions and pathlib.Path methods be tolerant to invalid paths. (#7695)

Such functions as os.path.exists(), os.path.lexists(), os.path.isdir(),
os.path.isfile(), os.path.islink(), and os.path.ismount() now return False
instead of raising ValueError or its subclasses UnicodeEncodeError
and UnicodeDecodeError for paths that contain characters or bytes
unrepresentative at the OS level.

Lib/genericpath.py

@@ -17,7 +17,7 @@ def exists(path):
     """Test whether a path exists.  Returns False for broken symbolic links"""
     try:
         os.stat(path)
-    except OSError:
+    except (OSError, ValueError):
         return False
     return True
 
@@ -28,7 +28,7 @@ def isfile(path):
     """Test whether a path is a regular file"""
     try:
         st = os.stat(path)
-    except OSError:
+    except (OSError, ValueError):
         return False
     return stat.S_ISREG(st.st_mode)
 
@@ -40,7 +40,7 @@ def isdir(s):
     """Return true if the pathname refers to an existing directory."""
     try:
         st = os.stat(s)
-    except OSError:
+    except (OSError, ValueError):
         return False
     return stat.S_ISDIR(st.st_mode)