hide psutil (#4013)

python/tvm/rpc/server.py

@@ -39,7 +39,6 @@ import subprocess
 import time
 import sys
 import signal
-import psutil
 
 from .._ffi.function import register_func
 from .._ffi.base import py_str
@@ -211,6 +210,7 @@ def _listen_loop(sock, port, rpc_key, tracker_addr, load_library, custom_addr):
         server_proc.join(opts.get("timeout", None))
         if server_proc.is_alive():
             logger.info("Timeout in RPC session, kill..")
+            import psutil
             parent = psutil.Process(server_proc.pid)
             # terminate worker childs
             for child in parent.children(recursive=True):