doc: use an absolute path in sys.path to work around a python DLL loading bug
This bug[1] was causing the zstd entry under "Available Compression Engines" to
be omitted from the documentation for some versions of python3. I could
upgrade, but past upgrades have broken venvs and clobbered installed packages.
It's a trivial workaround, so there's no sense in leaving this subtle issue. It
was flushed out by changing the module policy here from 'allow' to 'c', and
seeing this error:
ImportError: DLL load failed while importing parsers: The parameter is incorrect.
[1] https://github.com/python/cpython/issues/87271
Differential Revision: https://phab.mercurial-scm.org/D12599
syntax: glob
*.elc
*.tmp
*.orig
*.rej
*~
*.mergebackup
*.o
*.so
*.dll
*.exe
*.pyd
*.pyc
*.pyo
*$py.class
*.swp
*.prof
*.zip
\#*\#
.\#*
tests/artifacts/cache/big-file-churn.hg
tests/.coverage*
tests/.testtimes*
tests/.hypothesis
tests/hypothesis-generated
tests/annotated
tests/exceptions
tests/python3
tests/*.err
tests/htmlcov
build
contrib/chg/chg
contrib/hgsh/hgsh
contrib/vagrant/.vagrant
dist
packages
doc/common.txt
doc/*.[0-9]
doc/*.[0-9].txt
doc/*.[0-9].gendoc.txt
doc/*.[0-9].{x,ht}ml
MANIFEST
MANIFEST.in
patches
mercurial/__modulepolicy__.py
mercurial/__version__.py
mercurial/hgpythonlib.h
mercurial.egg-info
.DS_Store
tags
cscope.*
.vscode/*
.idea/*
.asv/*
.pytype/*
.mypy_cache
i18n/hg.pot
locale/*/LC_MESSAGES/hg.mo
hgext/__index__.py
rust/target/
rust/*/target/
# Generated wheels
wheelhouse/
syntax: rootglob
# See Profiling in rust/README.rst
.cargo/config
syntax: regexp
^\.pc/
^\.(pydev)?project
# hackable windows distribution additions
^hg-python
^hg.py$