1 files changed, 25 insertions, 3 deletions
diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py
index 1b3b430..fa99f56 100644
--- a/Lib/importlib/_bootstrap.py
+++ b/Lib/importlib/_bootstrap.py
@@ -878,13 +878,20 @@ def _find_spec_legacy(finder, name, path):
 
 def _find_spec(name, path, target=None):
     """Find a module's loader."""
-    if sys.meta_path is not None and not sys.meta_path:
+    meta_path = sys.meta_path
+    if meta_path is None:
+        # PyImport_Cleanup() is running or has been called.
+        raise ImportError("sys.meta_path is None, Python is likely "
+                          "shutting down")
+
+    if not meta_path:
         _warnings.warn('sys.meta_path is empty', ImportWarning)
+
     # We check sys.modules here for the reload case.  While a passed-in
     # target will usually indicate a reload there is no guarantee, whereas
     # sys.modules provides one.
     is_reload = name in sys.modules
-    for finder in sys.meta_path:
+    for finder in meta_path:
         with _ImportLockContext():
             try:
                 find_spec = finder.find_spec
@@ -925,6 +932,9 @@ def _sanity_check(name, package, level):
     if level > 0:
         if not isinstance(package, str):
             raise TypeError('__package__ not set to a string')
+        elif not package:
+            raise ImportError('attempted relative import with no known parent '
+                              'package')
         elif package not in sys.modules:
             msg = ('Parent module {!r} not loaded, cannot perform relative '
                    'import')
@@ -1033,7 +1043,19 @@ def _calc___package__(globals):
 
     """
     package = globals.get('__package__')
-    if package is None:
+    spec = globals.get('__spec__')
+    if package is not None:
+        if spec is not None and package != spec.parent:
+            _warnings.warn("__package__ != __spec__.parent "
+                           f"({package!r} != {spec.parent!r})",
+                           ImportWarning, stacklevel=3)
+        return package
+    elif spec is not None:
+        return spec.parent
+    else:
+        _warnings.warn("can't resolve package from __spec__ or __package__, "
+                       "falling back on __name__ and __path__",
+                       ImportWarning, stacklevel=3)
         package = globals['__name__']
         if '__path__' not in globals:
             package = package.rpartition('.')[0]