cbuild: change pytest invocation

[z-erica]

according to https://docs.pytest.org/en/7.1.x/how-to/usage.html#invoke-python, invoking pytest directly instead of doing python -m pytest does not implicitly add the cwd to sys.path. this could potentially help with packages with a test suite that has trouble being run from the source directory. since pytest is a shebang python script, we can just run it through the checkenv python executable

also set --import-path=append as in https://docs.pytest.org/en/7.1.x/explanation/pythonpath.html

list of python_pep517 packages without !check to retest:

• main/ansible-core
• main/magic-wormhole-mailbox-server
• main/mutagen
• main/python-b4
• main/python-bcrypt
• main/python-cattrs
• main/python-cryptography
• main/python-distlib
• main/python-jsonlines
• main/python-lxns
• main/python-mccabe
• main/python-passlib
• main/python-pretend
• main/python-pytest-env
• main/python-userpath
• main/python-resolvelib
• main/python-zipstream-ng
• main/python-pexpect
• main/python-mypy_extensions
• main/python-pytest-timeout
• main/libpwquality
• main/python-libevdev
• main/python-distutils-extra
• main/python-fonttools
• main/python-automat
• main/python-service-identity
• main/python-dkimpy
• main/python-openssl
• main/python-parso
• main/python-pytest-mock
• main/python-tap.py
• main/python-configobj
• main/python-cssselect
• main/python-jellyfish
• main/python-tldextract
• main/python-pygls
• main/python-pebble
• main/python-s3transfer
• main/python-pynacl
• main/python-lsp-jsonrpc
• main/python-ujson
• main/python-tqdm
• user/bmaptool
• main/python-digitalocean
• main/python-munkres
• main/python-jsonschema
• main/python-pytest-forked
• main/python-jedi
• main/python-fastjsonschema
• main/python-simplejson
• main/python-pytest-httpserver
• main/python-flask
• main/python-configargparse
• main/python-outcome
• main/python-appdirs
• main/python-chess
• main/python-pytest-subtests
• main/python-pybind11
• main/gallery-dl
• main/magic-wormhole-transit-relay
• main/python-dnspython
• main/python-magic
• main/python-pycparser
• main/python-markdown
• main/python-distro
• main/python-parsedatetime
• main/python-dasbus
• main/python-pycodestyle
• main/python-httplib2
• main/python-webencodings
• main/python-iterable-io
• main/python-lark-parser
• main/python-scour
• main/python-boto3
• main/python-acme
• main/python-jsonschema-specifications
• main/trash-cli
• main/python-mako
• main/python-blinker
• main/python-py-cpuinfo
• main/python-msgpack
• main/python-pyproject-metadata
• main/python-spake2
• user/python-bidict
• main/python-click
• main/python-requests-file
• user/python-sortedcollections
• main/python-lsp-server
• main/python-jmespath
• main/python-versioneer
• main/python-docstring-to-markdown
• main/python-jsonpickle
• main/python-meson
• main/python-colorama
• main/python-flask-login
• main/python-secretstorage
• main/virt-manager
• main/python-txtorcon
• main/python-josepy
• main/python-pyserial
• main/python-pykwalify
• main/python-pyelftools
• main/ruff
• main/python-dbusmock
• main/python-tomli
• main/python-pyasn1
• user/python-ssh2
• main/python-itsdangerous
• user/python-dbus-fast
• main/jinja2-cli
• main/python-treq
• user/asciinema
• main/ssh-audit
• main/python-pysol_cards
• main/python-sniffio
• main/python-smmap
• main/python-asgiref
• main/certbot
• main/python-u-msgpack
• main/python-pyasynchat
• user/protontricks
• main/python-pytest-xdist
• main/python-shtab
• main/python-pkgconfig
• main/python-hypothesis
• main/beets
• main/python-pyasn1_modules
• main/python-lsprotocol
• main/python-execnet
• main/python-mock
• main/python-vdf
• main/python-structlog
• main/python-rpds-py
• main/python-sh
• main/python-referencing
• main/python-pyyaml
• main/python-numpy
• main/python-pycryptodome
• main/python-tomli-w
• main/python-ptyprocess
• main/python-iso8601
• main/python-sortedcontainers
• main/python-testpath
• main/yt-dlp
• main/python-time-machine
• main/python-brotli
• main/python-flexmock
• main/python-astor
• main/python-freezegun
• main/lib_users
• main/python-docutils
• main/python-mediafile
• main/python-libvirt
• main/python-confuse
• main/python-pycryptodomex
• main/python-hyperlink
• main/python-random2
• main/python-pyflakes
• main/python-pyfuse3
• main/python-unidecode
• main/python-argcomplete
• main/python-lxml
• main/nicotine-plus
• main/python-musicbrainzngs
• main/borg
• main/python-dotenv
• main/python-pyhamcrest
• main/python-humanize
• main/python-gnupg
• main/python-pillow
• main/python-werkzeug
• main/python-cffi
• main/python-trio
• main/python-xlib
• main/nihtest