fix cuda check

python/paddle_serving_server_gpu/__init__.py

@@ -211,8 +211,13 @@ class Server(object):
             self.bin_path = os.environ["SERVING_BIN"]
 
     def check_cuda(self):
-        r = os.system("cat /usr/local/cuda/version.txt")
-        if r != 0:
+        cuda_flag = False
+        r = os.popen("whereis libcudart.so")
+        r = r.read().split(":")[1]
+        if "cudart" in r and os.system(
+                "ls /dev/ | grep nvidia > /dev/null") == 0:
+            cuda_flag = True
+        if not cuda_flag:
             raise SystemExit(
                 "CUDA not found, please check your environment or use cpu version by \"pip install paddle_serving_server\""
             )