fix for torch 1.7.0 error in tests

tests/python/frontend/pytorch/qnn_test.py

@@ -58,10 +58,8 @@ def get_qconfig(per_channel):
     from torch.quantization.observer import default_weight_observer
 
     if per_channel:
-        torch.backends.quantized.engine = "fbgemm"
         return torch.quantization.get_default_qconfig("fbgemm")
     else:
-        torch.backends.quantized.engine = "qnnpack"
         act = MovingAverageMinMaxObserver.with_args(reduce_range=False)
         return torch.quantization.QConfig(activation=act, weight=default_weight_observer)
 
@@ -298,7 +296,14 @@ def test_quantized_modules():
         raw_module.eval()
         inp = torch.rand(ishape)
 
-        quantize_model(raw_module, inp, per_channel=per_channel)
+        if module_name == "conv_transpose" and not is_version_greater_than("1.7.1"):
+            prev_engine = torch.backends.quantized.engine
+            torch.backends.quantized.engine = "qnnpack"
+            quantize_model(raw_module, inp, per_channel=per_channel)
+            torch.backends.quantized.engine = prev_engine
+        else:
+            quantize_model(raw_module, inp, per_channel=per_channel)
+
         script_module = torch.jit.trace(raw_module, inp).eval()
 
         with torch.no_grad():