sepolicy: use multiprocessing 'fork' method

'fork' was the default starting method in Python before 3.14 and it's
necessary for this code to work correctly

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2374569

    sh-5.2# sepolicy manpage -a -p /builddir/build/BUILD/selinux-policy-41.43-build/BUILDROOT/usr/share/man/man8/ -w -r /builddir/build/BUILD/selinux-policy-41.43-build/BUILDROOT
    ValueError: No SELinux Policy installed
    Exception ignored while calling deallocator <function Pool.__del__ at 0x7f36f9d333d0>:
    Traceback (most recent call last):
      File "/usr/lib64/python3.14/multiprocessing/pool.py", line 271, in __del__
        self._change_notifier.put(None)
      File "/usr/lib64/python3.14/multiprocessing/queues.py", line 397, in put
        self._writer.send_bytes(obj)
      File "/usr/lib64/python3.14/multiprocessing/connection.py", line 206, in send_bytes
        self._send_bytes(m[offset:offset + size])
      File "/usr/lib64/python3.14/multiprocessing/connection.py", line 444, in _send_bytes
        self._send(header + buf)
      File "/usr/lib64/python3.14/multiprocessing/connection.py", line 400, in _send
        n = write(self._handle, buf)
    BrokenPipeError: [Errno 32] Broken pipe

Signed-off-by: Petr Lautrbach <[email protected]>
Acked-by: James Carter <[email protected]>

Author: bachradsusi

python/sepolicy/sepolicy.py

@@ -25,7 +25,7 @@
 import sys
 import selinux
 import sepolicy
-from multiprocessing import Pool
+import multiprocessing
 from sepolicy import get_os_version, get_conditionals, get_conditionals_format_text
 import argparse
 PROGNAME = "selinux-python"
@@ -350,7 +350,8 @@ def manpage(args):
 
     manpage_domains = set()
     manpage_roles = set()
-    p = Pool()
+    multiprocessing.set_start_method('fork')
+    p = multiprocessing.Pool()
     async_results = []
     for domain in test_domains:
         async_results.append(p.apply_async(manpage_work, [domain, path, args.root, args.source_files, args.web]))