tests/import: Make import_override and pkg7 tests behave under CPython.

Signed-off-by: Damien George <damien@micropython.org>

tests/import/import_override.py

@@ -2,6 +2,10 @@
 
 
 def custom_import(name, globals, locals, fromlist, level):
+    # CPython always tries to import _io, so just let that through as-is.
+    if name == "_io":
+        return orig_import(name, globals, locals, fromlist, level)
+
     print("import", name, fromlist, level)
 
     class M:

tests/import/pkg7/subpkg1/subpkg2/mod3.py

@@ -5,7 +5,9 @@ print(mod1.foo)
 print(bar)
 
 # attempted relative import beyond top-level package
+# On older versions of CPython (eg 3.8) this is a ValueError, but on
+# newer CPython (eg 3.11) and MicroPython it's an ImportError.
 try:
     from .... import mod1
-except ImportError:
+except (ImportError, ValueError):
     print("ImportError")