Only replace readers if they're actually stdlib loaders/readers and not simply seemingly compatible instances.

Author: jaraco

importlib_resources/_compat.py

@@ -72,15 +72,21 @@ def _file_reader(spec):
             if path.exists():
                 return readers.FileReader(self)
 
+        def _is_stdlib_reader(spec):
+            return spec.loader.__class__.__module__.startswith('_frozen_importlib')
+
         return (
-            # local ZipReader if a zip module
-            _zip_reader(self.spec)
-            or
-            # local NamespaceReader if a namespace module
-            _namespace_reader(self.spec)
-            or
-            # local FileReader
-            _file_reader(self.spec)
+            _is_stdlib_reader(self.spec)
+            and (
+                # local ZipReader if a zip module
+                _zip_reader(self.spec)
+                or
+                # local NamespaceReader if a namespace module
+                _namespace_reader(self.spec)
+                or
+                # local FileReader
+                _file_reader(self.spec)
+            )
             or
             # native reader if it supplies 'files'
             _native_reader(self.spec)