[Deployment] Add deprecation message for deploy tool (open-mmlab#1483)

* master

* master 0721

* add README

* 1231 bump_version

* 0207 slowfast steplr

* 0207

* add deploy msg

tools/deployment/pytorch2onnx.py

@@ -1,5 +1,6 @@
 # Copyright (c) OpenMMLab. All rights reserved.
 import argparse
+import warnings
 
 import mmcv
 import numpy as np
@@ -168,3 +169,15 @@ def parse_args():
         show=args.show,
         output_file=args.output_file,
         verify=args.verify)
+
+    # Following strings of text style are from colorama package
+    bright_style, reset_style = '\x1b[1m', '\x1b[0m'
+    red_text, blue_text = '\x1b[31m', '\x1b[34m'
+    white_background = '\x1b[107m'
+
+    msg = white_background + bright_style + red_text
+    msg += 'DeprecationWarning: This tool will be deprecated in future. '
+    msg += blue_text + 'Welcome to use the unified model deployment toolbox '
+    msg += 'MMDeploy: https://github.com/open-mmlab/mmdeploy'
+    msg += reset_style
+    warnings.warn(msg)