add warn when import quant failed (#505)

paddleslim/quant/__init__.py

@@ -32,6 +32,7 @@ try:
     from .quanter import quant_aware, convert, quant_post_static, quant_post_dynamic
     from .quanter import quant_post, quant_post_only_weight
 except Exception as e:
+    _logger.warning(e)
     _logger.warning(
         "If you want to use training-aware and post-training quantization, "
         "please use Paddle >= 1.8.4 or develop version")