Check if docker is installed

labelme/cli/on_docker.py

 #!/usr/bin/env python
 
 import argparse
+import distutils.spawn
 import json
 import os
 import os.path as osp
@@ -9,6 +10,8 @@ import shlex
 import subprocess
 import sys
 
+from labelme import logger
+
 
 def get_ip():
     dist = platform.platform().split('-')[0]
@@ -80,6 +83,10 @@ def main():
     parser.add_argument('-O', '--output')
     args = parser.parse_args()
 
+    if not distutils.spawn.find_executable('docker'):
+        logger.error('Please install docker.')
+        sys.exit(1)
+
     try:
         out_file = labelme_on_docker(args.in_file, args.output)
         if out_file: