progress: use '%*d' to pad progress value Follows up 7f5108e58083. The problem of '% Nd' is that ' ' means we want {' ' or '-'} as a sign character. We should instead write '%Nd' to pad up to N characters with space, and N can be '*'.

py3: stringify IOError/OSError without loosing local character Follows up fa4d333cac58. An environment error may contain non-ascii characters on Windows, which should be encoded to a platform-native string.