py3: use pycompat.strkwargs() to convert kwargs keys to str before passing

py3: use '%d' instead of '%s' for integers Python 3 does not let you use '%s' for integers.

py3: pass the path in hg.repository() as bytes This make test-ancestor.py pass on Python 3.

py3: pass range() into list() to get one explicitly range() on python 3 returns a generator whereas on python 2 returns a list. So to get a list on python 3, we passed it into list()

check-concurrency: expose the feature as 'concurrent-push-mode' We move the feature to a proper configuration and document it. The config goes in the 'server' section because it feels like something the server owner would want to decide. We pick and open field because it seems likely that other checking levels will emerge in the future. (eg: server like the mozilla-try server will likely wants a "none" value) The option name contains 'push' since this affects 'push' only. The option value 'check-related' is preferred over one explicitly containing 'allow' or 'deny' because the client still have a strong decision power here. Here, the server is just advising the client on the check mode to use.

exchange: switch to usual way of testing for bundle2-ness We used safehasattr() in one place, but we use isinstance() for this everywhere else, so switch to the latter.

setup: update a comment that blamed py26 for a Windows workaround

i18n: drop a py25 conditional I'm not sure how to test this one. `make update-pot` spews all kinds of warnings, though it did before this change too.

perf: ensure HGRCPATH is exported on Windows After dropping the garbage collector hack, `hg perfstartup` started yelling about not being able to import the evolve extension, which I have in my user config. Launching `env` shows that an empty HGRCPATH isn't exported to the environment. Since `env` doesn't quote, I have no idea if the variable is trimmed, but Mercurial doesn't complain when processing it.

test-status: glob fixes for Windows