Try to remove database on -f

If the database is open (based on the presence of certain files), skip deletion.
There is a (very) small window where another process *could* try to open the database at the same time that it's being deleted, but it will then fail during the database setup with `sqlite3.OperationalError: disk I/O error`, but given the failure is immediate I think it's fine.

sbysrc/sby.py

@@ -22,7 +22,7 @@ import json, os, sys, shutil, tempfile, re
 from sby_cmdline import parser_func
 from sby_core import SbyConfig, SbyTask, SbyAbort, SbyTaskloop, process_filename, dress_message
 from sby_jobserver import SbyJobClient, process_jobserver_environment
-from sby_status import SbyStatusDb
+from sby_status import SbyStatusDb, remove_db, FileInUseError
 import time, platform, click
 
 release_version = 'unknown SBY version'
@@ -464,6 +464,12 @@ def start_task(taskloop, taskname):
                 print("*", file=gitignore)
         with open(f"{my_workdir}/status.path", "w") as status_path:
             print(my_status_db, file=status_path)
+        if os.path.exists(f"{my_workdir}/{my_status_db}") and opt_force:
+            try:
+                remove_db(f"{my_workdir}/{my_status_db}")
+            except FileInUseError:
+                # don't delete an open database
+                pass
 
     junit_ts_name = os.path.basename(sbyfile[:-4]) if sbyfile is not None else workdir if workdir is not None else "stdin"
     junit_tc_name = taskname if taskname is not None else "default"

sbysrc/sby_status.py

@@ -100,6 +100,10 @@ def transaction(method: Fn) -> Fn:
 
     return wrapper  # type: ignore
 
+class FileInUseError(Exception):
+    def __init__(self, *args, file: Path|str = "file"):
+        super().__init__(f"Found {file}, try again later", *args)
+
 
 class SbyStatusDb:
     def __init__(self, path: Path, task, timeout: float = 5.0, live_csv = False):
@@ -529,3 +533,11 @@ def filter_latest_task_ids(all_tasks: dict[int, dict[str]]):
     for task_id, task_dict in all_tasks.items():
         latest[task_dict["workdir"]] = task_id
     return list(latest.values())
+
+def remove_db(path):
+    path = Path(path)
+    lock_exts = [".sqlite-wal", ".sqlite-shm"]
+    for lock_file in [path.with_suffix(ext) for ext in lock_exts]:
+        if lock_file.exists():
+            raise FileInUseError(file=lock_file)
+    os.remove(path)