Fix bpo-42531: Teach importlib.resources.path to handle packages without __file__

Lib/importlib/resources.py

@@ -193,9 +193,11 @@ def path(package: Package, resource: Resource) -> Iterator[Path]:
         _check_location(package)
     # Fall-through for both the lack of resource_path() *and* if
     # resource_path() raises FileNotFoundError.
-    package_directory = Path(package.__spec__.origin).parent
-    file_path = package_directory / resource
-    if file_path.exists():
+    file_path = None
+    if package.__spec__.origin is not None:
+        package_directory = Path(package.__spec__.origin).parent
+        file_path = package_directory / resource
+    if file_path is not None and file_path.exists():
         yield file_path
     else:
         with open_binary(package, resource) as fp:

Lib/test/test_importlib/test_path.py

@@ -1,3 +1,4 @@
+from test.support import swap_attr
 import unittest
 
 from importlib import resources
@@ -26,6 +27,17 @@ class PathTests:
 class PathDiskTests(PathTests, unittest.TestCase):
     data = data01
 
+    def test_package_spec_origin_is_None(self):
+        import pydoc_data
+        spec = pydoc_data.__spec__
+        # Emulate importing from non-file source by setting spec.origin = None.
+        # Barge past path's sanity checks by ensuring spec.loader.is_resource
+        # returns False.
+        with swap_attr(spec, "origin", None), \
+            swap_attr(spec.loader, "is_resource", lambda *args: False), \
+            resources.path(pydoc_data, '_pydoc.css') as p:
+            pass
+
 
 class PathZipTests(PathTests, util.ZipSetup, unittest.TestCase):
     def test_remove_in_context_manager(self):