Use a utils.TempDir() decorator for temporary files, to make sure we clean up even in case of excep…

tools/utils.py

Index: tools/utils.py
diff --git a/tools/utils.py b/tools/utils.py
index 8346d09546c8f561856e91f463d2ede50a4fec1d..0abb0ed15d32240c5f8613e7612315830209f549 100644
--- a/tools/utils.py
+++ b/tools/utils.py
@@ -9,8 +9,10 @@ import commands
 import os
 import platform
 import re
+import shutil
 import subprocess
 import sys
+import tempfile
 
 
 # Try to guess the host operating system.
@@ -406,6 +408,18 @@ def DartSdkBinary():
   dart_binary_prefix = os.path.join(tools_dir, '..', 'sdk' , 'bin')
   return os.path.join(dart_binary_prefix, 'dart')
 
+class TempDir(object):
+  def __init__(self, prefix=''):
+    self._temp_dir = None
+    self._prefix = prefix
+
+  def __enter__(self):
+    self._temp_dir = tempfile.mkdtemp(self._prefix)
+    return self._temp_dir
+
+  def __exit__(self, *_):
+    shutil.rmtree(self._temp_dir, ignore_errors=True)
+
 
 if __name__ == "__main__":
   import sys