bundle2: convert ints to strings using pycompat.bytestring() Fixes some Python 3 regressions. We don't use %d here because the part id is actually an Optional[int]. It should always be initialized to a non-None value by the time this code executes, but we shouldn't blindly depend on that being the case. Differential Revision: https://phab.mercurial-scm.org/D272

#
# Avoid interference from actual test env:

unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL