Undo one change from str to unicode

This change was introduced by 2to3, but since the line is intended for
Python 2 only, it should still refer to unicode.

emsdk

@@ -692,7 +692,7 @@ class Tool:
   def __init__(self, data):
     # Convert the dictionary representation of the tool in 'data' to members of this class for convenience.
     for key in data:
-      if sys.version_info < (3,) and isinstance(data[key], str):
+      if sys.version_info < (3,) and isinstance(data[key], unicode):
         setattr(self, key, data[key].encode('Latin-1'))
       else:
         setattr(self, key, data[key])