Add an assert to ensure UTF-8 locale when handling file paths.

appengine/swarming/tools/start_servers.py

Index: appengine/swarming/tools/start_servers.py
diff --git a/appengine/swarming/tools/start_servers.py b/appengine/swarming/tools/start_servers.py
index b5c1cb29b474593fcbb439d913bf3ff82f5d3f7f..e694eb23569bd6160c5c0f3f53d5bd5a399b1d74 100755
--- a/appengine/swarming/tools/start_servers.py
+++ b/appengine/swarming/tools/start_servers.py
@@ -13,8 +13,13 @@ import tempfile
 
 
 APP_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+CLIENT_DIR = os.path.join(os.path.dirname(os.path.dirname(APP_DIR)), 'client')
 sys.path.insert(0, APP_DIR)
 
+sys.path.insert(0, CLIENT_DIR)
+from third_party.depot_tools import fix_encoding
+sys.path.pop(0)
+
 import test_env
 test_env.setup_test_env()
 
@@ -88,6 +93,7 @@ class LocalServers(object):
 
 
 def main():
+  fix_encoding.fix_encoding()
   parser = argparse.ArgumentParser(description=sys.modules[__name__].__doc__)
   parser.add_argument('-a', '--all', action='store_true')
   args = parser.parse_args()