py3: cast decode() argument to system string The actual types here may be mixed due to string literals and variables from other modules. So a cast is necessary. Differential Revision: https://phab.mercurial-scm.org/D2166

py3: avoid changing dictionary during iteration dict.items() and friends are iterators/views in Python 3. You aren't allowed to mutate the underlying dictionary when iterating on these views. So iterate over a copy of things. Differential Revision: https://phab.mercurial-scm.org/D2164