Add importlib.util.allowing_all_extensions().

Lib/importlib/util.py

@@ -112,6 +112,43 @@ def find_spec(name, package=None):
             return spec
 
 
+# Normally we would use contextlib.contextmanager.  However, this module
+# is imported by runpy, which means we want to avoid any unnecessary
+# dependencies.  Thus we use a class.
+
+class allowing_all_extensions:
+    """A context manager that lets users skip the compatibility check.
+
+    Normally, extensions that do not support multiple interpreters
+    may not be imported in a subinterpreter.  That implies modules
+    that do not implement multi-phase init.
+
+    Likewise for modules import in a subinterpeter with its own GIL
+    when the extension does not support a per-interpreter GIL.  This
+    implies the module does not have a Py_mod_multiple_interpreters slot
+    set to Py_MOD_PER_INTERPRETER_GIL_SUPPORTED.
+
+    In both cases, this context manager may be used to temporarily
+    disable the check for compatible extension modules.
+    """
+
+    def __init__(self, enabled):
+        self.enabled = enabled
+
+    def __enter__(self):
+        self.old = _imp._override_multi_interp_extensions_check(self.override)
+        return self
+
+    def __exit__(self, *args):
+        old = self.old
+        del self.old
+        _imp._override_multi_interp_extensions_check(old)
+
+    @property
+    def override(self):
+        return 1 if self.enabled else 0
+
+
 class _LazyModule(types.ModuleType):
 
     """A subclass of the module type which triggers loading upon attribute access."""

Lib/test/support/import_helper.py

@@ -115,6 +115,8 @@ def multi_interp_extensions_check(enabled=True):
     It overrides the PyInterpreterConfig.check_multi_interp_extensions
     setting (see support.run_in_subinterp_with_config() and
     _xxsubinterpreters.create()).
+
+    Also see importlib.utils.allowing_all_extensions().
     """
     old = _imp._override_multi_interp_extensions_check(1 if enabled else -1)
     try: