use skipif_acls_not_working decorator for freebsd also

use platform-specific ACLs to check.
for unsupported platform, just return False.

src/borg/testsuite/platform.py

@@ -31,13 +31,22 @@ def are_acls_working():
     with unopened_tempfile() as filepath:
         open(filepath, "w").close()
         try:
-            access = b"user::rw-\ngroup::r--\nmask::rw-\nother::---\nuser:root:rw-:9999\ngroup:root:rw-:9999\n"
+            if is_freebsd:
+                access = b"user::rw-\ngroup::r--\nmask::rw-\nother::---\nuser:root:rw-\n"
+                contained = b"user:root:rw-"
+            elif is_linux:
+                access = b"user::rw-\ngroup::r--\nmask::rw-\nother::---\nuser:root:rw-:0\n"
+                contained = b"user:root:rw-:0"
+            elif is_darwin:
+                return True  # improve?
+            else:
+                return False  # unsupported platform
             acl = {"acl_access": access}
             acl_set(filepath, acl)
             read_acl = {}
             acl_get(filepath, read_acl, os.stat(filepath))
             read_acl_access = read_acl.get("acl_access", None)
-            if read_acl_access and b"user::rw-" in read_acl_access:
+            if read_acl_access and contained in read_acl_access:
                 return True
         except PermissionError:
             pass

src/borg/testsuite/platform_freebsd.py

@@ -2,7 +2,7 @@ import os
 import tempfile
 
 from ..platform import acl_get, acl_set
-from .platform import skipif_not_freebsd
+from .platform import skipif_not_freebsd, skipif_acls_not_working
 
 # set module-level skips
 pytestmark = [skipif_not_freebsd]
@@ -46,6 +46,7 @@ def set_acl(path, access=None, default=None, nfs4=None, numeric_ids=False):
     acl_set(path, item, numeric_ids=numeric_ids)
 
 
+@skipif_acls_not_working
 def test_access_acl():
     file1 = tempfile.NamedTemporaryFile()
     set_acl(
@@ -82,6 +83,7 @@ def test_access_acl():
     assert b"group:9999:rw-" in acl_access_ids
 
 
+@skipif_acls_not_working
 def test_default_acl():
     tmpdir = tempfile.mkdtemp()
     set_acl(tmpdir, access=ACCESS_ACL, default=DEFAULT_ACL)