PY-20125 Epydoc formatter also uses explicit UTF-8 encoding to communicate with the IDE

PY-20125 Epydoc formatter also uses explicit UTF-8 encoding to communicate with the IDE

Also I've fixed several problems in epydoc_formatter.py helper:
1. ParseError.is_fatal() should accept one argument (self) since it's
normal class method.
2. Python errors are reported with full stacktrace so it's easier
to find out an error in the helper itself. Unfortunately, it's not
possible to recover traces for exception objects stored in errors list.