Refactor _PurePath to not use PurePath internals

  - Add attribute _path_module to _PurePath and its
    subclasses in order to process path normalization

xmlschema/resources.py

@@ -9,6 +9,8 @@
 #
 import copy
 import os.path
+import ntpath
+import posixpath
 import platform
 import re
 import string
@@ -45,13 +47,12 @@ class _PurePath(PurePath):
     A version of pathlib.PurePath adapted for managing the creation
     from URIs and the simple normalization of paths.
     """
-    _from_parts: Any
-    _flavour: Any
+    _path_module = os.path
 
     def __new__(cls, *args: str) -> '_PurePath':
         if cls is _PurePath:
             cls = _PureWindowsPath if os.name == 'nt' else _PurePosixPath
-        return cast('_PurePath', cls._from_parts(args))
+        return super().__new__(cls, *args)
 
     @classmethod
     def from_uri(cls, uri: str) -> '_PurePath':
@@ -98,12 +99,21 @@ def from_uri(cls, uri: str) -> '_PurePath':
 
     def as_uri(self) -> str:
         if not self.is_absolute():
-            uri: str = self._flavour.make_uri(self)
-            while uri.startswith('file:/'):
-                uri = uri.replace('file:/', 'file:', 1)
-            return uri
+            # Converts relative paths to not RFC 8089 compliant relative
+            # file URIs because urlopen() doesn't accept simple paths
+            drive = self.drive
+            if len(drive) == 2 and drive[1] == ':':
+                prefix = 'file:' + drive
+                path = self.as_posix()[2:]
+            elif drive:
+                prefix = 'file:'
+                path = self.as_posix()
+            else:
+                prefix = 'file:'
+                path = str(self)
+            return prefix + quote_from_bytes(os.fsencode(path))
 
-        uri = cast(str, self._flavour.make_uri(self))
+        uri = super().as_uri()
         if isinstance(self, _PureWindowsPath) and str(self).startswith(r'\\'):
             # UNC format case: use the format where the host part is included
             # in the path part, to let urlopen() works.
@@ -112,15 +122,17 @@ def as_uri(self) -> str:
         return uri
 
     def normalize(self) -> '_PurePath':
-        normalized_path = self._flavour.pathmod.normpath(str(self))
-        return cast('_PurePath', self._from_parts((normalized_path,)))
+        normalized_path = self._path_module.normpath(str(self))
+        return self.__class__(normalized_path)
 
 
 class _PurePosixPath(_PurePath, PurePosixPath):
+    _path_module = posixpath
     __slots__ = ()
 
 
 class _PureWindowsPath(_PurePath, PureWindowsPath):
+    _path_module = ntpath
     __slots__ = ()