rust-cpython: add stub wrapper that'll prevent leaked data from being mutated In order to allow mutation of PySharedRefCell value while PyLeaked reference exists, we need yet another "borrow" scope where mutation is prohibited. try_borrow<'a> and try_borrow_mut<'a> defines the "borrow" scope <'a>. The subsequent patches will implement leak counter based on this scope. PyLeakedRef<T> and PyLeakedRefMut<T> could be unified to PyLeakedRef<&T> and PyLeakedRef<&mut T> respectively, but I didn't do that since it seemed a bit weird that deref_mut() would return a mutable reference to an immutable reference.

rust-cpython: rename PyLeakedRef to PyLeaked This series will make PyLeaked* behave more like a Python iterator, which means mutation of the owner object will be allowed and the leaked reference (i.e. the iterator) will be invalidated instead. I'll add PyLeakedRef/PyLeakedRefMut structs which will represent a "borrowed" state, and prevent the underlying value from being mutably borrowed while the leaked reference is in use: let shared = self.inner_shared(py); let leaked = shared.leak_immutable(); { let leaked_ref: PyLeakedRef<_> = leaked.borrow(py); shared.borrow_mut(); // panics since the underlying value is borrowed } shared.borrow_mut(); // allowed The relation between PyLeaked* structs is quite similar to RefCell/Ref/RefMut, but the implementation can't be reused because the borrowing state will have to be shared across objects having no lifetime relation. PyLeaked isn't named as PyLeakedCell since it isn't actually a cell in that leaked.borrow_mut() will require &mut self.

py3: don't use bytes with vars() or __dict__ Inspired by D7227. These were all the remaining instances I could find. Differential Revision: https://phab.mercurial-scm.org/D7230

Added signature for changeset ca3dca416f8d

Added tag 5.2 for changeset ca3dca416f8d

py3: add inline comment about encoding issue of str(Abort())

py3: do not reimplement Abort.__str__() on Python 2 It isn't necessary on Python 2, and the default implementation should be better than our BaseException_str() clone.

tests: write out file using bytes I/O The encoding of sys.stdout varies between Python versions. So using a one-liner to write a file from a Unicode string is not deterministic. This commit writes out the file using bytes I/O to ensure we have exactly the bytes we want in the file. This change fixes a test failure in Python 3.5/3.6. Differential Revision: https://phab.mercurial-scm.org/D7226

import-checker: open all source files as utf-8 Before, we opened in text mode and used the default encoding to interpret the bytes within. This caused problems interpreting some byte sequences in some files. This commit changes things to always open files as UTF-8, which makes the error go away. test-check-module-imports.t now passes on Python 3.5 and 3.6 with this change. Differential Revision: https://phab.mercurial-scm.org/D7225

localrepo: use str for lookup in vars() vars() returns a dict of str. So always use a native str for the key lookup. Differential Revision: https://phab.mercurial-scm.org/D7227

automation: install python3-venv Debian package Debian's python install has a crippled venv by default, as it is lacking ensurepip. When you try to run `python3 -m venv` it tells you to install `python3-venv`. So this commit does that in our automation environment so we can fully test installing Mercurial using venv+pip with the system Python. Differential Revision: https://phab.mercurial-scm.org/D7229

tests: look for ensurepip before using venv Debian appears to cripple the venv module by default by removing the associated ensurepip functionality. (The module isn't present at all.) This caused test-install.t to fail when using the Debian python3 unless the python3-venv package was installed. This commit introduces a new hghave requirement for detecting ensurepip and makes the Python 3 install variant conditional on its presence. This should make test-install.t pass when using an incomplete Debian Python. Differential Revision: https://phab.mercurial-scm.org/D7228

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.

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