borg with-lock: catch exception, print error msg, fixes #8022

src/borg/archiver/lock_cmds.py

@@ -4,7 +4,7 @@ import subprocess
 from ._common import with_repository
 from ..cache import Cache
 from ..constants import *  # NOQA
-from ..helpers import prepare_subprocess_env, set_ec
+from ..helpers import prepare_subprocess_env, set_ec, CommandError
 from ..manifest import Manifest
 
 from ..logger import create_logger
@@ -35,6 +35,8 @@ class LocksMixIn:
             # we exit with the return code we get from the subprocess
             rc = subprocess.call([args.command] + args.args, env=env)
             set_ec(rc)
+        except (FileNotFoundError, OSError, ValueError) as e:
+            raise CommandError(f"Error while trying to run '{args.command}': {e}")
         finally:
             # we need to commit the "no change" operation we did to the manifest
             # because it created a new segment file in the repository. if we would

src/borg/testsuite/archiver/lock_cmds.py

@@ -18,3 +18,10 @@ def test_with_lock(archivers, request):
     lock_path = os.path.join(archiver.repository_path, "lock.exclusive")
     command = "python3", "-c", 'import os, sys; sys.exit(42 if os.path.exists("%s") else 23)' % lock_path
     cmd(archiver, "with-lock", *command, fork=True, exit_code=42)
+
+
+def test_with_lock_non_existent_command(archivers, request):
+    archiver = request.getfixturevalue(archivers)
+    cmd(archiver, "rcreate", RK_ENCRYPTION)
+    command = ["non_existent_command"]
+    cmd(archiver, "with-lock", *command, fork=True, exit_code=EXIT_ERROR)