Cache/retrieve extracted CIPD packages in local isolate cache

client/utils/fs.py

Index: client/utils/fs.py
diff --git a/client/utils/fs.py b/client/utils/fs.py
index c743f2b7f4a5d27bad146319a1f0656c5f7c263a..cda292ea6c6040933af3f826a0c2534ec8ab0ee7 100644
--- a/client/utils/fs.py
+++ b/client/utils/fs.py
@@ -34,8 +34,8 @@ if sys.platform == 'win32':
     """Adds '\\\\?\\' when given an absolute path so the MAX_PATH (260) limit is
     not enforced.
     """
-    assert os.path.isabs(path), path
-    assert isinstance(path, unicode), path
+    assert os.path.isabs(path), '%r must be absolute' % path
+    assert isinstance(path, unicode), '%r must be unicode' % path
     prefix = u'\\\\?\\'
     return path if path.startswith(prefix) else prefix + path
 
@@ -121,8 +121,8 @@ else:
     In some rare case, concatenating str and unicode may cause a
     UnicodeEncodeError because the default encoding is 'ascii'.
     """
-    assert os.path.isabs(path), path
-    assert isinstance(path, unicode), path
+    assert os.path.isabs(path), '%r must be absolute' % path
+    assert isinstance(path, unicode), '%r must be unicode' % path
     return path.encode('utf-8')