zdtm.py: add an option to change pycriu import path

By default zdtm expects that criu is built from source first and only
then you can run zdtm tests against it. But what if you really want to
run tests against a criu version installed on the system? Yes there is
already a nice option for zdtm to change the criu binary it uses
"--criu-bin", but it would still end up using the pycriu module from
source and you would still have to build everything beforehand.

Let's add an option to change the path where zdtm searches for pycriu
module "--pycriu-search-path". This way we can run zdtm tests on the
criu installed on the system directly without building criu from source,
e.g. on Fedora it works like:

test/zdtm.py run --criu-bin /usr/sbin/criu \
  --pycriu-search-path /usr/lib/python3.13/site-packages \
  -t zdtm/static/env00

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>

test/zdtm.py

@@ -22,11 +22,11 @@ import sys
 import tempfile
 import time
 import uuid
+import site
 from builtins import input, int, open, range, str, zip
 
 import yaml
 
-import pycriu as crpc
 from zdtm.criu_config import criu_config
 
 # File to store content of streamed images
@@ -1142,6 +1142,24 @@ class criu:
         self.__img_streamer_process = None
         self.__tls = self.__tls_options() if opts['tls'] else []
         self.__criu_bin = opts['criu_bin']
+
+        global crpc
+        pycriu_search_path = opts.get('pycriu_search_path')
+        if pycriu_search_path:
+            sys.path.insert(0, pycriu_search_path)
+
+        try:
+            import pycriu as crpc
+            if pycriu_search_path:
+                print(f"pycriu loaded from: {crpc.__file__}")
+        except ImportError:
+            if not pycriu_search_path:
+                print("Consider building CRIU or using '--pycriu-search-path' option.")
+            raise
+        finally:
+            if pycriu_search_path:
+                sys.path.pop(0)
+
         self.__crit_bin = opts['crit_bin']
         self.__pre_dump_mode = opts['pre_dump_mode']
         self.__preload_libfault = bool(opts['preload_libfault'])
@@ -2169,7 +2187,8 @@ class Launcher:
               'dedup', 'sbs', 'freezecg', 'user', 'dry_run', 'noauto_dedup',
               'remote_lazy_pages', 'show_stats', 'lazy_migrate', 'stream',
               'tls', 'criu_bin', 'crit_bin', 'pre_dump_mode', 'mntns_compat_mode',
-              'rootless', 'preload_libfault', 'mocked_cuda_checkpoint')
+              'rootless', 'preload_libfault', 'mocked_cuda_checkpoint',
+              'pycriu_search_path')
         arg = repr((name, desc, flavor, {d: self.__opts[d] for d in nd}))
 
         if self.__use_log:
@@ -2860,6 +2879,9 @@ def get_cli_args():
     rp.add_argument("--criu-bin",
                     help="Path to criu binary",
                     default='../criu/criu')
+    rp.add_argument("--pycriu-search-path",
+                    help=f"Path to search for pycriu module first (e.g., {site.getsitepackages()[0]})",
+                    default=None)
     rp.add_argument("--crit-bin",
                     help="Path to crit binary",
                     default='../crit/crit')