[test] Set default locale in test runner

tools/run-tests.py

 #!/usr/bin/env python
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 362 matching lines @@
   """Convert buildbot build configs to configs understood by the v8 runner.
 
   V8 configs are always lower case and without the additional _x64 suffix for
   64 bit builds on windows with ninja.
   """
   mode = config[:-4] if config.endswith('_x64') else config
   return mode.lower()
 
 def SetupEnvironment(options):
   """Setup additional environment variables."""
+
+  # Many tests assume an English interface.
+  os.environ['LANG'] = 'en_US.UTF-8'
+
   symbolizer = 'external_symbolizer_path=%s' % (
       os.path.join(
           BASE_DIR, 'third_party', 'llvm-build', 'Release+Asserts', 'bin',
           'llvm-symbolizer',
       )
   )
 
   if options.asan:
     os.environ['ASAN_OPTIONS'] = symbolizer
 
@@ skipping 440 matching lines @@
         "--coverage-dir=%s" % options.sancov_dir])
     except:
       print >> sys.stderr, "Error: Merging sancov files failed."
       exit_code = 1
 
   return exit_code
 
 
 if __name__ == "__main__":
   sys.exit(Main())