gnu: python-backpack: Fix build.

* gnu/packages/python-xyz.scm (python-backpack)[native-inputs]: Add python-toml.

gnu: python-simplejson: Update to 3.17.2, fixing build.

* gnu/packages/python-xyz.scm (python-simplejson): Update to 3.17.2.
[native-inputs]: Add python-toml.

gnu: python-babel: Fix build.

* gnu/packages/python-xyz.scm (python-babel)[source]: Re-indent.
[native-inputs]: Add tzdata-for-tests.

gnu: python-3.9: Add a search path specification for PYTHONTZPATH.

Python 3.9 implemented PEP 615 (<)https://www.python.org/dev/peps/pep-0615/>),
which relies on either a compiled time default value or the PYTHONTZPATH
environment variable to find the system tzdata database.

* gnu/packages/python.scm (python-3.9)[native-search-paths]: Add a new search
path specification for PYTHONTZPATH.

gnu: python-pympler: Update to 0.9.

* gnu/packages/python-xyz.scm (python-pympler): Update to 0.9.

gnu: python-pytest-forked: Update to 1.3.0.

* gnu/packages/check.scm (python-pytest-forked): Update to 1.3.0.
[propagated-inputs]: Move python-pytest to...
[native-inputs]: ... here.

gnu: python-typed-ast: Update to 1.4.2.

* gnu/packages/python-xyz.scm (python-typed-ast): Update to 1.4.2.

gnu: python-mccabe: Fix indentation.

* gnu/packages/python-xyz.scm (python-mccabe): Fix indentation.

gnu: python-pyflakes: Fix build.

* gnu/packages/patches/python-pyflakes-fix-tests.patch: Add patch.
* gnu/local.mk (dist_patch_DATA): Register it.
* gnu/packages/python-xyz.scm (python-pyflakes)[patches]: Apply it.
[home-page]: Update.

gnu: python-mccabe: Add missing python-toml input.

* gnu/packages/python-xyz.scm (python-mccabe)[native-inputs]: Add python-toml.
[home-page]: Update home page.

gnu: python-pytest: Propagate python-iniconfig, python-toml.

Based on a reading of the install_requires field of its setup.cfg file.

* gnu/packages/check.scm (python-pytest)[native-inputs]: Move
python-iniconfig...
[propagated-inputs]: ... to here.  Add python-toml.  Remove
python-atomicwrites, apparently only required on the win32 platform.

gnu: python-mypy: Fix build.

This follows commit b5ccc6cc9a, which updated python-pytest to version 6 and
removed the python-pytest-6 variable.

* gnu/packages/python-check.scm (python-mypy)
[native-inputs]: Rename python-pytest-6 to python-pytest.

gnu: python-decorator: Update to 4.4.2.

* gnu/packages/python-xyz.scm (python-decorator): Update to 4.4.2.

gnu: Add python-pypa-build.

* gnu/packages/python-build.scm (python-pypa-build): New variable.

gnu: python-xyz: Move a few modules to (gnu packages python-build).

* gnu/packages/python-xyz.scm (python-pep517): Inherit from
python-pep517-bootstrap.  Remove the inherited common fields.
(python-poetry-core, python-wheel)
(python-toml): Move to ...
* gnu/packages/python-build.scm: ... here, a new module.
(python-pep517-bootstrap): New package.
* gnu/local.mk (GNU_SYSTEM_MODULES): Register the new module.

build-system/gnu: Really ignore the return value of phases.

This is a followup to 04baa011e9122205009d6d5f15b8162bf6f3fb8a.

* guix/build/gnu-build-system.scm (gnu-build): Really ignore the return
value of PROC.  Wrap PROC call in 'with-throw-handler'.  Add
'end-of-phase' procedure and use it.

gnu: tar: Update to 1.33.

* gnu/packages/base.scm (tar): Update to 1.33.

gnu: findutils: Update to 4.8.0.

* gnu/packages/base.scm (findutils): Update to 4.8.0.
[source](patches): Remove "findutils-test-rwlock-threads.patch".
* gnu/packages/patches/findutils-test-rwlock-threads.patch: Remove.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/commencement.scm (findutils-boot0)[arguments]: Add
'skip-fnmatch-test' phase.

gnu: ed: Update to 1.17.

* gnu/packages/ed.scm (ed): Update to 1.17.

gnu: zstd: Add missing slash in 'libzstd.pc'.

Fixes a regression introduced in
959a397d220ad49b5193feb84b036220313fb9c7, whereby directory names in
'libzstd.pc' would lack a slash after $prefix.

* gnu/packages/compression.scm (zstd)[arguments]: In
'adjust-library-locations' phase, add trailing slash for $prefix in .pc
file.