py3: fully fix bundlepart.__repr__ to return str not bytes My previous fix did not fully fix the issue: it would attempt to use %-formatting to combine two strs into a bytes, which won't work. Let's just switch the entire function to operating in strs. This can cause a small output difference that will likely not be noticed since no one noticed that the method wasn't working at all before: if `id` or `type` are not-None, they'll be shown as `b'val'` instead of `val`. Since this is a debugging aid and these strings shouldn't be shown to the user, slightly rough output is most likely fine and it's likely not worthwhile to add the necessary conditionals to marginally improve it. Differential Revision: https://phab.mercurial-scm.org/D8091