Fix doctest module loading to avoid double-creation of modules

implementations/python/tests/test_doctests.py

@@ -1,17 +1,17 @@
 import doctest
 import pkgutil
-import importlib.util
+import importlib
 
 import preserves
 
 def load_tests(loader, tests, ignore):
-    def m(spec):
-        mod = importlib.util.module_from_spec(spec)
-        mod.__loader__.exec_module(mod)
+    mods = []
+    mods.append(preserves)
+    for mi in pkgutil.iter_modules(preserves.__path__, preserves.__name__ + '.'):
+        mod = importlib.import_module(mi.name)
+        mods.append(mod)
+
+    for mod in mods:
         tests.addTests(doctest.DocTestSuite(mod))
-    spec = preserves.__spec__
-    m(spec)
-    for mi in pkgutil.walk_packages(spec.submodule_search_locations, spec.name + '.'):
-        subspec = mi.module_finder.find_spec(mi.name)
-        m(subspec)
+
     return tests