tests: port inline extension in test-convert-cvs.t to py3
# skip-blame two b prefixes, nothing more
Differential Revision: https://phab.mercurial-scm.org/D3483
minirst: fix bytes slicing defect on Python 3
This is the only lingering problem in minirst on Python
3. test-minirst.py now passes on Python 3.
Differential Revision: https://phab.mercurial-scm.org/D3478