buildchain, docs, salt, tests: run pip-compile

Due to changes in `pluggy` (a dependency of `pytest`) using the
`importlib.metadata` module from the standard library instead of the
`importlib-metadata` package when running on Python >= 3.8, we need to
pin the `basepython` used in the `pip-compile` Tox env to the version
that's actually used in CI, otherwise `pip` complains during
installation of dependencies the `importlib-metadata` package is not
listed (with hashes) in some `requirements.txt`. As such, setting
`basepython` to `python3.6`, similar to 8a9104b.

Also, update the versions of `pip` and `pip-tools` used in the
`pip-compile` `tox` target, and use the `--allow-unsafe` flag which is
supposedly not really unsafe at all (and will become the default).

Finally, since we're currently unable to properly update the MacOS X
platform-specific dependencies for the buildchain (in
`buildchain/requirements-Darwin.txt`), the updates to
`buildchain/requirements-Linux.txt` are manually reverted (after running
`tox -e pip-compile` on a Linux host) to ensure both
`buildchain/requirements-Linux.txt` and
`buildchain/requirements-Darwin.txt` remain in sync (except for
`pyinotify` and `macfsevents`, as usual).

See: 8a9104b
Closes: #2897
Closes: #2898
See: pytest-dev/pluggy#222
See: https://github.com/pytest-dev/pluggy/pull/223/files#diff-60f61ab7a8d1910d86d9fda2261620314edcae5894d5aaa236b821c7256badd7
See: jazzband/pip-tools#806 (comment)
See: #2986 (comment)

buildchain/requirements-dev.txt

@@ -4,13 +4,13 @@
 #
 #    tox -e pip-compile
 #
-astroid==2.3.3 \
-    --hash=sha256:71ea07f44df9568a75d0f354c49143a4575d90645e9fead6dfb52c26a85ed13a \
-    --hash=sha256:840947ebfa8b58f318d42301cf8c0a20fd794a33b61cc4638e28e9e61ba32f42 \
+astroid==2.4.2 \
+    --hash=sha256:2f4078c2a41bf377eea06d71c9d2ba4eb8f6b1af2135bec27bbbb7d8f12bb703 \
+    --hash=sha256:bc58d83eb610252fd8de6363e39d4f1d0619c894b0ed24603b881c02e64c7386 \
     # via pylint
-isort==4.3.21 \
-    --hash=sha256:54da7e92468955c4fceacd0c86bd0ec997b0e1ee80d97f67c35a78b719dccab1 \
-    --hash=sha256:6e811fcb295968434526407adb8796944f1988c5b65e8139058f2014cbe100fd \
+isort==5.6.4 \
+    --hash=sha256:dcab1d98b469a12a1a624ead220584391648790275560e1a43e54c5dceae65e7 \
+    --hash=sha256:dcaeec1b5f0eca77faea2a35ab790b4f3680ff75590bfcb7145986905aab2f58 \
     # via pylint
 lazy-object-proxy==1.4.3 \
     --hash=sha256:0c4b206227a8097f05c4dbdd323c50edf81f15db3b8dc064d08c62d37e1a504d \
@@ -57,46 +57,62 @@ mypy==0.740 \
     --hash=sha256:d5bf0e6ec8ba346a2cf35cb55bf4adfddbc6b6576fcc9e10863daa523e418dbb \
     --hash=sha256:d7574e283f83c08501607586b3167728c58e8442947e027d2d4c7dcd6d82f453 \
     --hash=sha256:dc889c84241a857c263a2b1cd1121507db7d5b5f5e87e77147097230f374d10b \
-    --hash=sha256:f4748697b349f373002656bf32fede706a0e713d67bfdcf04edf39b1f61d46eb
+    --hash=sha256:f4748697b349f373002656bf32fede706a0e713d67bfdcf04edf39b1f61d46eb \
+    # via -r buildchain/requirements-dev.in
 pyenchant==2.0.0 \
     --hash=sha256:b9526fc2c5f1ba0637e50200b645a7c20fb6644dbc6f6322027e7d2fbf1084a5 \
     --hash=sha256:e8000144e61551fcab9cd1b6fdccdded20e577e8d6d0985533f0b2b9c38fd952 \
-    --hash=sha256:fc31cda72ace001da8fe5d42f11c26e514a91fa8c70468739216ddd8de64e2a0
-pylint==2.4.4 \
-    --hash=sha256:3db5468ad013380e987410a8d6956226963aed94ecb5f9d3a28acca6d9ac36cd \
-    --hash=sha256:886e6afc935ea2590b462664b161ca9a5e40168ea99e5300935f6591ad467df4
-six==1.14.0 \
-    --hash=sha256:236bdbdce46e6e6a3d61a337c0f8b763ca1e8717c03b369e87a7ec7ce1319c0a \
-    --hash=sha256:8f3cd2e254d8f793e7f3d6d9df77b92252b52637291d0f0da013c76ea2724b6c \
+    --hash=sha256:fc31cda72ace001da8fe5d42f11c26e514a91fa8c70468739216ddd8de64e2a0 \
+    # via -r buildchain/requirements-dev.in
+pylint==2.6.0 \
+    --hash=sha256:bb4a908c9dadbc3aac18860550e870f58e1a02c9f2c204fdf5693d73be061210 \
+    --hash=sha256:bfe68f020f8a0fece830a22dd4d5dddb4ecc6137db04face4c3420a46a52239f \
+    # via -r buildchain/requirements-dev.in
+six==1.15.0 \
+    --hash=sha256:30639c035cdb23534cd4aa2dd52c3bf48f06e5f4a941509c8bafd8ce11080259 \
+    --hash=sha256:8b74bedcbbbaca38ff6d7491d76f2b06b3592611af620f8426e82dddb04a5ced \
     # via astroid
+toml==0.10.2 \
+    --hash=sha256:806143ae5bfb6a3c6e736a764057db0e6a0e05e338b5630894a5f779cabb4f9b \
+    --hash=sha256:b3bda1d108d5dd99f4a20d24d9c348e91c4db7ab1b749200bded2f839ccbe68f \
+    # via pylint
 typed-ast==1.4.1 \
     --hash=sha256:0666aa36131496aed8f7be0410ff974562ab7eeac11ef351def9ea6fa28f6355 \
     --hash=sha256:0c2c07682d61a629b68433afb159376e24e5b2fd4641d35424e462169c0a7919 \
+    --hash=sha256:0d8110d78a5736e16e26213114a38ca35cb15b6515d535413b090bd50951556d \
     --hash=sha256:249862707802d40f7f29f6e1aad8d84b5aa9e44552d2cc17384b209f091276aa \
     --hash=sha256:24995c843eb0ad11a4527b026b4dde3da70e1f2d8806c99b7b4a7cf491612652 \
     --hash=sha256:269151951236b0f9a6f04015a9004084a5ab0d5f19b57de779f908621e7d8b75 \
+    --hash=sha256:3742b32cf1c6ef124d57f95be609c473d7ec4c14d0090e5a5e05a15269fb4d0c \
     --hash=sha256:4083861b0aa07990b619bd7ddc365eb7fa4b817e99cf5f8d9cf21a42780f6e01 \
     --hash=sha256:498b0f36cc7054c1fead3d7fc59d2150f4d5c6c56ba7fb150c013fbc683a8d2d \
     --hash=sha256:4e3e5da80ccbebfff202a67bf900d081906c358ccc3d5e3c8aea42fdfdfd51c1 \
     --hash=sha256:6daac9731f172c2a22ade6ed0c00197ee7cc1221aa84cfdf9c31defeb059a907 \
     --hash=sha256:715ff2f2df46121071622063fc7543d9b1fd19ebfc4f5c8895af64a77a8c852c \
     --hash=sha256:73d785a950fc82dd2a25897d525d003f6378d1cb23ab305578394694202a58c3 \
+    --hash=sha256:7e4c9d7658aaa1fc80018593abdf8598bf91325af6af5cce4ce7c73bc45ea53d \
     --hash=sha256:8c8aaad94455178e3187ab22c8b01a3837f8ee50e09cf31f1ba129eb293ec30b \
     --hash=sha256:8ce678dbaf790dbdb3eba24056d5364fb45944f33553dd5869b7580cdbb83614 \
+    --hash=sha256:92c325624e304ebf0e025d1224b77dd4e6393f18aab8d829b5b7e04afe9b7a2c \
     --hash=sha256:aaee9905aee35ba5905cfb3c62f3e83b3bec7b39413f0a7f19be4e547ea01ebb \
+    --hash=sha256:b52ccf7cfe4ce2a1064b18594381bccf4179c2ecf7f513134ec2f993dd4ab395 \
     --hash=sha256:bcd3b13b56ea479b3650b82cabd6b5343a625b0ced5429e4ccad28a8973f301b \
     --hash=sha256:c9e348e02e4d2b4a8b2eedb48210430658df6951fa484e59de33ff773fbd4b41 \
     --hash=sha256:d205b1b46085271b4e15f670058ce182bd1199e56b317bf2ec004b6a44f911f6 \
     --hash=sha256:d43943ef777f9a1c42bf4e552ba23ac77a6351de620aa9acf64ad54933ad4d34 \
     --hash=sha256:d5d33e9e7af3b34a40dc05f498939f0ebf187f07c385fd58d591c533ad8562fe \
+    --hash=sha256:d648b8e3bf2fe648745c8ffcee3db3ff903d0817a01a12dd6a6ea7a8f4889072 \
+    --hash=sha256:f208eb7aff048f6bea9586e61af041ddf7f9ade7caed625742af423f6bae3298 \
+    --hash=sha256:fac11badff8313e23717f3dada86a15389d0708275bddf766cca67a84ead3e91 \
     --hash=sha256:fc0fea399acb12edbf8a628ba8d2312f583bdbdb3335635db062fa98cf71fca4 \
+    --hash=sha256:fcf135e17cc74dbfbc05894ebca928ffeb23d9790b3167a674921db19082401f \
     --hash=sha256:fe460b922ec15dd205595c9b5b99e2f056fd98ae8f9f56b888e7a17dc2b757e7 \
     # via astroid, mypy
-typing-extensions==3.7.4.2 \
-    --hash=sha256:6e95524d8a547a91e08f404ae485bbb71962de46967e1b71a0cb89af24e761c5 \
-    --hash=sha256:79ee589a3caca649a9bfd2a8de4709837400dfa00b6cc81962a1e6a1815969ae \
-    --hash=sha256:f8d2bd89d25bc39dabe7d23df520442fa1d8969b82544370e03d88b5a591c392 \
+typing-extensions==3.7.4.3 \
+    --hash=sha256:7cb407020f00f7bfc3cb3e7881628838e69d8f3fcab2f64742a5e76b2f841918 \
+    --hash=sha256:99d4073b617d30288f569d3f13d2bd7548c3a7e4c8de87db09a9d29bb3a4a60c \
+    --hash=sha256:dafc7639cde7f1b6e1acc0f457842a83e722ccca8eef5270af2d74792619a89f \
     # via mypy
-wrapt==1.11.2 \
-    --hash=sha256:565a021fd19419476b9362b05eeaa094178de64f8361e44468f9e9d7843901e1 \
+wrapt==1.12.1 \
+    --hash=sha256:b62ffa81fb85f4332a4f609cab4ac40709470da05643a082ec1eb88e6d9b97d7 \
     # via astroid

docs/requirements.txt

@@ -4,46 +4,50 @@
 #
 #    tox -e pip-compile
 #
--e git+https://github.com/scality/[email protected]#egg=sphinx_scality
+-e git+https://github.com/scality/[email protected]#egg=sphinx_scality  # via -r docs/requirements.in
 alabaster==0.7.12         # via sphinx
 babel==2.9.0              # via sphinx
-certifi==2020.11.8        # via requests
-chardet==3.0.4            # via doc8, requests
-colorama==0.4.4
-doc8==0.8.1
+certifi==2020.12.5        # via requests
+chardet==4.0.0            # via doc8, requests
+colorama==0.4.4           # via -r docs/requirements.in
+doc8==0.8.1               # via -r docs/requirements.in
 docutils==0.16            # via doc8, restructuredtext-lint, sphinx, sphinxcontrib-github-alt
 httplib2==0.18.1          # via plantuml
 idna==2.10                # via requests
 imagesize==1.2.0          # via sphinx
-importlib-metadata==3.1.0  # via sphinxcontrib-spelling, stevedore
+importlib-metadata==3.3.0  # via sphinxcontrib-spelling, stevedore
 jinja2==2.11.2            # via sphinx
 livereload==2.6.3         # via sphinx-autobuild
 markupsafe==1.1.1         # via jinja2
-packaging==20.4           # via sphinx
+packaging==20.8           # via sphinx
 pbr==5.5.1                # via stevedore
-plantuml==0.3.0
-pyenchant==3.1.1          # via sphinxcontrib-spelling
-pygments==2.7.2           # via doc8, sphinx
+plantuml==0.3.0           # via -r docs/requirements.in
+pyenchant==3.2.0          # via sphinxcontrib-spelling
+pygments==2.7.3           # via doc8, sphinx
 pyparsing==2.4.7          # via packaging
 pytz==2020.4              # via babel
-pyyaml==5.3.1
-requests==2.25.0          # via sphinx
+pyyaml==5.3.1             # via -r docs/requirements.in
+requests==2.25.1          # via sphinx
 restructuredtext-lint==1.3.2  # via doc8
-six==1.15.0               # via doc8, livereload, packaging
+six==1.15.0               # via doc8, livereload
 snowballstemmer==2.0.0    # via sphinx
-sphinx-autobuild==2020.9.1
-sphinx-rtd-theme==0.5.0
-sphinx==3.3.1
+sphinx-autobuild==2020.9.1  # via -r docs/requirements.in
+sphinx-rtd-theme==0.5.0   # via -r docs/requirements.in
+sphinx==3.3.1             # via -r docs/requirements.in, sphinx-autobuild, sphinx-rtd-theme, sphinx-scality, sphinxcontrib-github-alt, sphinxcontrib-plantuml, sphinxcontrib-spelling
 sphinxcontrib-applehelp==1.0.2  # via sphinx
 sphinxcontrib-devhelp==1.0.2  # via sphinx
-sphinxcontrib-github-alt==1.2
+sphinxcontrib-github-alt==1.2  # via -r docs/requirements.in
 sphinxcontrib-htmlhelp==1.0.3  # via sphinx
 sphinxcontrib-jsmath==1.0.1  # via sphinx
-sphinxcontrib-plantuml==0.19
+sphinxcontrib-plantuml==0.19  # via -r docs/requirements.in
 sphinxcontrib-qthelp==1.0.3  # via sphinx
 sphinxcontrib-serializinghtml==1.1.4  # via sphinx
-sphinxcontrib-spelling==7.1.0
-stevedore==3.2.2          # via doc8
+sphinxcontrib-spelling==7.1.0  # via -r docs/requirements.in
+stevedore==3.3.0          # via doc8
 tornado==6.1              # via livereload
+typing-extensions==3.7.4.3  # via importlib-metadata
 urllib3==1.26.2           # via requests
 zipp==3.4.0               # via importlib-metadata
+
+# The following packages are considered to be unsafe in a requirements file:
+setuptools==51.0.0        # via sphinx