Python3: replace distutils with sysconfig

- `distutils` module is long time deprecated and already deleted
  from the CPython mainline.

- To remain compatible with Debian/Ubuntu Python3 packaging style,
  try
  `distutils.sysconfig.get_python_path(0,0)`
  first with fallback on
  `sysconfig.get_path('purelib')`

- pyzfs_unittest suite is run unconditionally as a part of ZTS.

- Add pyzfs_unittest suite to sanity tests.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: szubersk <szuberskidamian@gmail.com>
Closes #12833 
Closes #13280 
Closes #14177

tests/runfiles/sanity.run

@@ -624,3 +624,7 @@ tags = ['functional', 'zvol', 'zvol_swap']
 [tests/functional/zpool_influxdb]
 tests = ['zpool_influxdb']
 tags = ['functional', 'zpool_influxdb']
+
+[tests/functional/pyzfs]
+tests = ['pyzfs_unittest']
+tags = ['functional', 'pyzfs']

tests/test-runner/bin/zts-report.py.in

@@ -61,14 +61,6 @@ known_reason = 'Known issue'
 #
 exec_reason = 'Test user execute permissions required for utilities'
 
-#
-# Some tests require a minimum python version of 3.6 and will be skipped when
-# the default system version is too old.  There may also be tests which require
-# additional python modules be installed, for example python3-cffi is required
-# by the pyzfs tests.
-#
-python_deps_reason = 'Python modules missing: python3-cffi'
-
 #
 # Some tests require that the kernel supports renameat2 syscall.
 #
@@ -232,7 +224,6 @@ maybe = {
     'io/mmap': ['SKIP', fio_reason],
     'largest_pool/largest_pool_001_pos': ['FAIL', known_reason],
     'mmp/mmp_on_uberblocks': ['FAIL', known_reason],
-    'pyzfs/pyzfs_unittest': ['SKIP', python_deps_reason],
     'pool_checkpoint/checkpoint_discard_busy': ['FAIL', 11946],
     'projectquota/setup': ['SKIP', exec_reason],
     'removal/removal_condense_export': ['FAIL', known_reason],

tests/zfs-tests/tests/functional/pyzfs/pyzfs_unittest.ksh.in

@@ -18,6 +18,8 @@
 
 if [ -n "$ASAN_OPTIONS" ]; then
 	export LD_PRELOAD=$(ldd "$(command -v zfs)" | awk '/libasan\.so/ {print $3}')
+	# ASan reports leaks in CPython 3.10
+	ASAN_OPTIONS="$ASAN_OPTIONS:detect_leaks=false"
 fi
 
 #
@@ -30,20 +32,6 @@ fi
 #
 
 verify_runnable "global"
-
-# Verify that the required dependencies for testing are installed.
-@PYTHON@ -c "import cffi" 2>/dev/null ||
-	log_unsupported "python3-cffi not found by Python"
-
-# We don't just try to "import libzfs_core" because we want to skip these tests
-# only if pyzfs was not installed due to missing, build-time, dependencies; if
-# we cannot load "libzfs_core" due to other reasons, for instance an API/ABI
-# mismatch, we want to report it.
-@PYTHON@ -c '
-import pkgutil, sys
-sys.exit(pkgutil.find_loader("libzfs_core") is None)' ||
-	log_unsupported "libzfs_core not found by Python"
-
 log_assert "Verify the nvlist and libzfs_core Python unittest run successfully"
 
 # log_must buffers stderr, which interacts badly with