errors: remove ParseError.args With the previous few patches, it is no longer needed (as far as the test suite can tell anyway). Differential Revision: https://phab.mercurial-scm.org/D9354

errors: let ParseError use Abort.__bytes__ The function is no longer used anywhere as far as our tests can tell, so there's no need to have a custom version of it. Differential Revision: https://phab.mercurial-scm.org/D9353

config: clean up message about ignored untrusted config The error message relied on Python's default formatting of arguments to an Exception's constructor. Let's try to make it a little more readable for users. Differential Revision: https://phab.mercurial-scm.org/D9352

tests: use new ParseError.format() in test-trusted.py Differential Revision: https://phab.mercurial-scm.org/D9351

errors: make ParseError a subtype of Abort I didn't plan this before, but the previous two changes made it really easy to make `ParseError` a subtype of `Abort`. It seems obvious with hindsight that I *should* have planned it :) Differential Revision: https://phab.mercurial-scm.org/D9350

tests: make doctests not depend on str(ParseError()) format `ParseError` implements `__bytes__`, but it doesn't implement `__str__`, so it gets the default `__str__` implementation. The next patch will make it so `ParseError` gets a `__str__` implementation, which changes the format slightly. This prepares by making us not depend on the format. Differential Revision: https://phab.mercurial-scm.org/D9349

errors: format "abort: " text in a new Abort.format() method This remove some duplication we had. Differential Revision: https://phab.mercurial-scm.org/D9348

errors: make formatparse() an instance method on ParseError It's just a little simpler this way. Don't ask me what the "hg: " prefix signifies to the user, I just left it as it was. I think we should consider changing the prefixes later (maybe always use "abort: ", or maybe use more specific prefixes in general). Differential Revision: https://phab.mercurial-scm.org/D9347