[DATALAD RUNCMD] also install psutil for testing of datalad

[yarikoptic]

I believe that it is a reason for the https://github.com/datalad/datalad/issues/5918 and I will also fix at datalad side to skip that portion of the test if no psutil is installed, but here we better make it testable.

I also tried just adding [devel] to pip install git+https://... url but that does not work

[jwodder]

@yarikoptic For the record, I believe the only way to specify extras when installing from a Git URL is to write datalad[devel] @ git+https://github.com/datalad/datalad@${commitish}.

[yarikoptic]

awesome

seems to work

```shell lena:/tmp $> py=3; d=venvs/dev$py; virtualenv --python=python$py $d && source $d/bin/activate && python3 -m pip install datalad[devel]@git+https://github.com/yarikoptic/datalad@bf-delete-credential ... Successfully installed BeautifulSoup4-4.9.3 Jinja2-3.0.1 MarkupSafe-2.0.1 Pillow-8.3.1 PyGithub-1.55 PyYAML-5.4.1 Pygments-2.10.0 SecretStorage-3.3.1 alabaster-0.7.12 annexremote-1.5.0 appdirs-1.4.4 argcomplete-1.12.3 asv-0.4.2 babel-2.9.1 boto-2.49.0 certifi-2021.5.30 cffi-1.14.6 chardet-4.0.0 charset-normalizer-2.0.4 citeproc-py-0.6.0 coverage-5.5 cryptography-3.4.7 datalad-0.14.6+60.g3cddd7c4a deprecated-1.2.12 distro-1.6.0 docutils-0.16 duecredit-0.9.1 exifread-2.3.2 fasteners-0.16.3 future-0.18.2 gprof2dot-2021.2.21 httpretty-1.1.4 humanize-3.11.0 idna-3.2 imagesize-1.2.0 importlib-metadata-4.6.4 iso8601-0.1.16 jeepney-0.7.1 jsmin-2.2.2 keyring-23.1.0 keyrings.alt-4.1.0 lxml-4.6.3 msgpack-1.0.2 multidict-5.1.0 mutagen-1.45.1 nose-1.3.7 nose-timer-1.0.1 packaging-21.0 patool-1.12 psutil-5.8.0 pycparser-2.20 pyjwt-2.1.0 pynacl-1.4.0 pypandoc-1.6.3 pyparsing-2.4.7 pyperclip-1.8.2 python-dateutil-2.8.2 python-gitlab-2.10.0 python-xmp-toolkit-2.0.1 pytz-2021.1 requests-2.26.0 requests-ftp-0.3.1 requests-toolbelt-0.9.1 simplejson-3.17.3 six-1.16.0 snowballstemmer-2.1.0 soupsieve-2.2.1 sphinx-4.1.2 sphinx-rtd-theme-0.5.2 sphinxcontrib-applehelp-1.0.2 sphinxcontrib-devhelp-1.0.2 sphinxcontrib-htmlhelp-2.0.0 sphinxcontrib-jsmath-1.0.1 sphinxcontrib-qthelp-1.0.3 sphinxcontrib-serializinghtml-1.1.5 tqdm-4.62.1 urllib3-1.26.6 vcrpy-4.1.1 whoosh-2.7.4 wrapt-1.12.1 yarl-1.6.3 zipp-3.5.0 ```

so I will RF template to just do that instead of manual installation of test depends

[yarikoptic]

eh, I guess I have opened the pandora's box by installing more of python libraries which might need

libxmp.ExempiLoadError: Exempi library not found.

for that will push installing exempi on osx and linux. Windows fail in test_get_open_files is a surprise (now it fails since we do install psutils so it is not skipped) since doesn't fail in "stock" datalad tests... "fun"

[yarikoptic]

screw it -- not time to please windows