Update faiss.py (#387)

update faiss.py to enforce less strict check of error message

faiss.py

@@ -21,7 +21,7 @@ try:
     from swigfaiss_gpu import *
 except ImportError as e:
 
-    if e.args[0] != 'ImportError: No module named swigfaiss_gpu':
+    if 'No module named' not in e.args[0]:
         # swigfaiss_gpu is there but failed to load: Warn user about it.
         sys.stderr.write("Failed to load GPU Faiss: %s\n" % e.args[0])
         sys.stderr.write("Faiss falling back to CPU-only.\n")