tests/micropython/import_mpy_invalid.py: Skip if target cant import mpy.

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

tests/micropython/import_mpy_invalid.py

@@ -3,6 +3,7 @@
 try:
     import sys, io, vfs
 
+    sys.implementation._mpy
     io.IOBase
 except (ImportError, AttributeError):
     print("SKIP")