Check if os.__file__ is available before using it (#1944)

* check if os.file is available before using it

* use threading.__file__ als last fallback

Author: timrid

src/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_filtering.py

@@ -155,7 +155,8 @@ def _get_default_library_roots(cls):
 
         # Make sure we always get at least the standard library location (based on the `os` and
         # `threading` modules -- it's a bit weird that it may be different on the ci, but it happens).
-        roots.append(os.path.dirname(os.__file__))
+        if hasattr(os, "__file__"):
+            roots.append(os.path.dirname(os.__file__))
         roots.append(os.path.dirname(threading.__file__))
         if IS_PYPY:
             # On PyPy 3.6 (7.3.1) it wrongly says that sysconfig.get_path('stdlib') is

src/debugpy/_vendored/pydevd/pydevd_file_utils.py

@@ -88,7 +88,14 @@ def _get_library_dir():
                 break
 
     if library_dir is None or not os_path_exists(library_dir):
-        library_dir = os.path.dirname(os.__file__)
+        if hasattr(os, "__file__"):
+            # "os" is a frozen import an thus "os.__file__" is not always set.
+            # See https://github.com/python/cpython/pull/28656
+            library_dir = os.path.dirname(os.__file__)
+        else:
+            # "threading" is not a frozen import an thus "threading.__file__" is always set.
+            import threading
+            library_dir = os.path.dirname(threading.__file__)
 
     return library_dir