Sanity check that 'localhost' can be resolved before building Observatory

tools/observatory_tool.py

 #!/usr/bin/env python
 # Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 """Helper for building and deploying Observatory"""
 
 import argparse
 import os
 import platform
 import shutil
+import socket
 import subprocess
 import sys
 import utils
 
 SCRIPT_DIR = os.path.dirname(sys.argv[0])
 DART_ROOT = os.path.realpath(os.path.join(SCRIPT_DIR, '..'))
 PUB_PATH = os.path.join(DART_ROOT, 'third_party', 'pkg',
                         'pub', 'bin', 'pub.dart')
 IGNORE_PATTERNS = shutil.ignore_patterns(
     '*.map',
@@ skipping 189 matching lines @@
                       options.silent)
   elif (cmd == 'deploy'):
     Deploy('build', 'deployed')
   elif (cmd == 'rewrite'):
     RewritePubSpec(args[0], args[1], args[2], args[3])
   else:
     print >> sys.stderr, ('ERROR: command "%s" not supported') % (cmd)
     return -1;
 
 def main():
+  # Sanity check that localhost can be resolved.
+  try:
+    socket.gethostbyname('localhost')
+  except:
+    print("The hostname 'localhost' could not be resolved. Please fix your"
+          "/etc/hosts file and try again")
+    return -1
   # Parse the options.
   parser = BuildArguments()
   (options, args) = parser.parse_known_args()
   if not ProcessOptions(options, args):
     parser.print_help()
     return 1
   # Calculate absolute paths before changing directory.
   if (options.dart_executable != None):
     options.dart_executable = os.path.abspath(options.dart_executable)
   if (options.pub_executable != None):
     options.pub_executable = os.path.abspath(options.pub_executable)
   if (options.pub_snapshot != None):
     options.pub_snapshot = os.path.abspath(options.pub_snapshot)
   if (options.stamp != ''):
     options.stamp = os.path.abspath(options.stamp)
   if len(args) == 1:
     args[0] = os.path.abspath(args[0])
   # Pub must be run from the project's root directory.
   ChangeDirectory(options.directory)
   result = ExecuteCommand(options, args)
   if result == 0:
     CreateTimestampFile(options)
   return result
 
 
 if __name__ == '__main__':
   sys.exit(main());