py3: fix the way we produce bytes list in store.py bytes(range(127)) does not produce a list whereas we need a list. This patch fixes that.

py3: convert os.__file__ to bytes os.__file__ returns unicode path on Python 3. We need to have bytespath. This patch uses pycompat.fsencode() to encode unicode path to bytes path.

commandserver: handle backlog before exiting Previously, when a chg server is exiting, it does not handle connected clients so clients may get ECONNRESET and crash: 1. client connect() # success 2. server shouldexit = True and exit 3. client recv() # ECONNRESET d7875bfbfccb makes this race condition easier to reproduce if a lot of short chg commands are started in parallel. This patch fixes the above issue by unlinking the socket path to stop queuing new connections and processing all pending connections before exit.

commandserver: prevent unlink socket twice This patch changes unixforkingservice so it only calls `self._servicehandler.unlinksocket(self.address)` at most once. This is needed by the next patch.

runtests: check ports on IPv6 address Previously, checkportisavailable only checks ports on the IPv4 address. This patch makes it check IPv6 as well. It'll be useful if "localhost" does not have an IPv4 address, or its IPv4 address does not exist somehow.

zeroconf: fail nicely on IPv6 only system zeroconf only knows how to deal with IPv4; I develop on a system where the only IPv4 address is 127.0.0.1. Teach zeroconf to ignore IPv6 addresses when looking for plausible IPv4 connectivity.

chg: verify XDG_RUNTIME_DIR According to the specification [1], $XDG_RUNTIME_DIR should be ignored unless: The directory MUST be owned by the user, and he MUST be the only one having read and write access to it. Its Unix access mode MUST be 0700. This patch adds a check and ignores it if it does not meet part of the criteria. [1]: https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

check-code: permit functools.reduce