Fix unittest dataset error (#16925)

python/paddle/fluid/tests/unittests/CMakeLists.txt

@@ -88,11 +88,11 @@ py_test_modules(test_warpctc_op MODULES test_warpctc_op ENVS FLAGS_warpctc_dir=$
 py_test_modules(test_bilinear_interp_op MODULES test_bilinear_interp_op SERIAL)
 py_test_modules(test_nearest_interp_op MODULES test_nearest_interp_op SERIAL)
 py_test_modules(test_imperative_resnet MODULES test_imperative_resnet ENVS
-  FLAGS_cudnn_deterministic=1)
+    FLAGS_cudnn_deterministic=1 SERIAL)
 py_test_modules(test_imperative_mnist MODULES test_imperative_mnist ENVS
-  FLAGS_cudnn_deterministic=1)
+    FLAGS_cudnn_deterministic=1 SERIAL)
 py_test_modules(test_imperative_se_resnext MODULES test_imperative_se_resnext ENVS
-  FLAGS_cudnn_deterministic=1 SERIAL)
+    FLAGS_cudnn_deterministic=1 SERIAL)
 
 if(WITH_DISTRIBUTE)
     py_test_modules(test_dist_train MODULES test_dist_train SERIAL)
@@ -103,7 +103,7 @@ if(WITH_DISTRIBUTE)
         py_test_modules(test_dist_se_resnext MODULES test_dist_se_resnext)
         py_test_modules(test_dgc_op MODULES test_dgc_op)
         set_tests_properties(test_dist_se_resnext PROPERTIES TIMEOUT 1000)
-        py_test_modules(test_dist_se_resnext_nccl MODULES test_dist_se_resnext_nccl)
+        py_test_modules(test_dist_se_resnext_nccl MODULES test_dist_se_resnext_nccl SERIAL)
         set_tests_properties(test_dist_se_resnext_nccl PROPERTIES TIMEOUT 1000)
         # FIXME(typhoonzero): add these tests back
         # py_test_modules(test_dist_transformer MODULES test_dist_transformer)