automation: avoid '~' in the temp directory on Windows If a long-ish username is used, the environment variable ends up with a '~' to be 8.3 path compatible. That in turn causes a handful of tests (mostly ssh related) to add quotes around $TESTMP. I have no AWS experience, so I have no idea if this is the proper way to do it. But I've hit this problem locally, and redirecting the directory is a workaround. I don't recall if the directory is created on demand by the test harness, but presumably if this is configured before the machine boots, Windows will do it for us. Differential Revision: https://phab.mercurial-scm.org/D7130

tests: use venv on Python 3 This test was failing in some Python 3 environments because `$PYTHON -m virtualenv` was somehow resulting in Python 2 being used. Why, I'm not sure. Python 3 includes virtualenv in the standard library as the `venv` module. This commit changes test-install.t to use `$PYTHON -m venv` on Python 3 and `$PYTHON -m virtualenv` on Python 2 (if available). I chose to make some test output duplicated because we can't have nested conditionals and there is no easy way to express ORing of hghave checks. Differential Revision: https://phab.mercurial-scm.org/D7224

tests: remove HGALLOWPYTHON3 reference This variable was removed from setup.py in c3e10f705a6c. Differential Revision: https://phab.mercurial-scm.org/D7223

run-tests: use byte strings for inserted output We were inserting str on Python 3 which resulted in mixed str/bytes types on the list. This would later blow up when trying to write str to the .err file opened in bytes mode. Differential Revision: https://phab.mercurial-scm.org/D7222

contrib: require Python 3.7 for byteify-strings.py bb509f39d387 made an error, it's actually 3.7 that introduced token.COMMENT. Differential Revision: https://phab.mercurial-scm.org/D7220

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.