hghave: fix bytes/string issue on Python 3

packaging: add support for CentOS 8 The resulting executable has not been tested in detail yet. I ran 'hg version' and 'hg clone', which worked fine (except for extensions acting up due to Python 3). Differential Revision: https://phab.mercurial-scm.org/D7216

packaging: allow choosing python version depending on centos version Differential Revision: https://phab.mercurial-scm.org/D7217

fsmonitor: use stringutil.forcebytestr() instead of str() on an exception Similar to 5fa8ac91190e / D7206, should get test-install.t passing on py3. Differential Revision: https://phab.mercurial-scm.org/D7218

py3: add a __str__ method to Abort This improves the rendering of some exceptions by avoiding raw bytestrings, especially when using --traceback option.

py3: add Python 3 exception output to test-lfs-serve-access.t Similar to a973a75e92bf or 3e9c6cef949b.

automation: install black This should unblock us from running the code formatting test in our automated environment. Differential Revision: https://phab.mercurial-scm.org/D7197

py3: use %d to format an int Avoids a TypeError under py3. Fortunately this is very much an edge case since it requires the user to have deliberately created a local tag of the form 'D\d+' that isn't truthful. Differential Revision: https://phab.mercurial-scm.org/D7215

fsmonitor: normalize exception types to bytes Unavailable.msg should now always be bytes. We also rename Unavailable.__str__ to __bytes__ as it always returns bytes. We make __str__ a simple wrapper that decodes that result to str. There's probably some excessive strutil.forcebytestr() in fsmonitor/__init__.py now. But at least the exceptions around type coercion should now be gone. Differential Revision: https://phab.mercurial-scm.org/D7214

fsmonitor: normalize clock value to bytes We normalize the value returned by watchman because we perform a number of compares with this value in code. So the easiest path forward is to normalize to bytes so we don't have to update many call sites. With this commit, the fsmonitor extension appears to be working with Python 3! Although there are still some failures in edge cases... Differential Revision: https://phab.mercurial-scm.org/D7213

fsmonitor: use next() instead of .next() This is needed for Python 3 compatibility. Differential Revision: https://phab.mercurial-scm.org/D7212

fsmonitor: normalize Watchman paths to bytes Otherwise it will be a str on Python 3 and operations below which operate in the bytes domain will fail. Differential Revision: https://phab.mercurial-scm.org/D7211

fsmonitor: handle unicode keys in tuples In Python 3, keys in the bset tuple are typically str, not bytes. PyBytes_AsString() would return NULL. But we weren't checking the return value and this would lead to a segfault. This commit makes the code type and Python version aware. The Python version specific code is to allow us to utilize a modern API for converting str -> char* without having to allocate an extra PyObject. FWIW I wanted to assume that keys were always str. However, there appear to be some bytes keys in some cases. I haven't debugged this further. Differential Revision: https://phab.mercurial-scm.org/D7210

fsmonitor: make _hashignore compatible with Python 3 The Hasher wants a bytes but we were feeding it a str. Let's use our repr() implementation to return bytes. In addition, the hexdigest() would return a str, which would be compared against a bytes and would always fail. Normalize to bytes so the compare works. Differential Revision: https://phab.mercurial-scm.org/D7209

fsmonitor: normalize hostname to bytes Without this, we get a str/bytes mismatching when using % formatting a few lines below. Differential Revision: https://phab.mercurial-scm.org/D7208

fsmonitor: access repo.root There is no repo._root. It looks like fsmonitor has been busted since this access was introduced in ab1900323b1 in July 2019! Differential Revision: https://phab.mercurial-scm.org/D7207

fsmonitor: coerce watchman exception to bytes Without this, we get errors due to passing str to a function which expects bytes. Differential Revision: https://phab.mercurial-scm.org/D7206

fsmonitor: fix str/bytes mismatch when accessing watchman version There were 2 bugs here. First, keys in the tuple are always str. Second, we needed to normalize the value to bytes to prevent a str/bytes mismatch on Python 3. With this commit, `hg debuginstall` with fsmonitor enabled now works on Python 3. Differential Revision: https://phab.mercurial-scm.org/D7205

fsmonitor: reapply b1f62cd39b5c The recent revendoring of pywatchman undid this changeset. Let's reapply it. This commit was generated by running `hg graft -f b1f62cd39b5c`. It applied cleanly. Differential Revision: https://phab.mercurial-scm.org/D7204

fsmonitor: reapply dd35abc409ee The recent revendoring of pywatchman undid this bug fix. Let's reapply it. Differential Revision: https://phab.mercurial-scm.org/D7203

fsmonitor: remove pywatchman from exclusion rule The recently vendored pywatchman code base is now formatted with black. We can now remove pywatchman from our black exclusion rule. Differential Revision: https://phab.mercurial-scm.org/D7202

fsmonitor: refresh pywatchman with upstream This commit vendors pywatchman commit 259dc66dc9591f9b7ce76d0275bb1065f390c9b1 from upstream without modifications. The previously vendored pywatchman from changeset 16f4b341288d was from Git commit c77452. This commit effectively undoes the following Mercurial changesets: * dd35abc409ee fsmonitor: correct an error message * b1f62cd39b5c fsmonitor: layer on another hack in bser.c for os.stat() compat (issue5811) * c31ce080eb75 py3: convert arguments, cwd and env to native strings when spawning subprocess * 876494fd967d cleanup: delete lots of unused local variables * 57264906a996 watchman: add the possibility to set the exact watchman binary location The newly-vendored code has support for specifying the binary location, so 57264906a996 does not need applied. But we do need to modify our code to specify a proper argument name. 876494fd967d is not important, so it will be ignored. c31ce080eb75 globally changed the code base to always pass str to subprocess. But pywatchman's code is Python 3 clean, so we don't need to do this. This leaves dd35abc409ee and b1f62cd39b5c, which will be re-applied in subsequent commits. Differential Revision: https://phab.mercurial-scm.org/D7201

py3: encode strings before setting rev summary in gnuarch converter

py3: use raw string to query EmailMessage in gnuarch converter

py3: use mail.parsebytes() in gnuarch catlog parser We drop 'catlogparser' attribute now unused.

tests: handle Message-Id line wrapping in test-notify-changegroup.t This fixes this test on Python 3 with a long hostname. See changeset 4128ffba4431 for details.

py3: define and use json.loads polyfill Python 3.5's json.loads() requires a str. Only Python 3.6+ supports passing a bytes or bytearray. This commit implements a json.loads() polyfill on Python 3.5 so that we can use bytes. The added function to detect encodings comes verbatim from Python 3.7.

contrib: require Python 3.6 for byteify-strings.py This script makes use of `token.COMMENT`, which apparently isn't present until Python 3.6. So make the script and its test conditional on Python 3.6.

demandimportpy3: only use lazy extension loader on Python 3.6+ There was an inline comment denoting a bug in the lazy extension loader on Python 3.5 which prevents it from working there. But the code was not conditional on the Python version. The result of this was a myriad of failures on Python 3.5 due to getattr() and friends not working on lazy extension modules. By making extension modules non-lazy on Python 3.5, we reduce the number of test failures from 48 to 22 on that Python version.

ui: flush before prompting for input with readline I was using `hg absorb` with Python 3 and noticed that the prompt was appearing without any output about what would be done. After I answered the prompt, the output was printed to stdout. This appears to be a buffering difference between Python 2 and Python 3. To work around it, this commit adds an explicit flush() before calling the raw input function when readline is used.