tests: remove output conditionalized on no-py3
I simply did a search for `^.* \(no-py3 !\)\n` and removed all
matched lines. There are still some references to no-py3. But these
were the simpler ones to match against.
Differential Revision: https://phab.mercurial-scm.org/D12253
py3: use io.BytesIO directly
Previously, pycompat.bytesio and pycompat.stringio referred to
io.BytesIO. And util.bytesio and util.stringio aliased the pycompat
symbols.
This commit switches everything to use io.BytesIO directly. util.bytesio
and util.stringio still exist to provide backwards compatibility, as
they were the preferred symbols.
Differential Revision: https://phab.mercurial-scm.org/D12252