unlock stale locks before forgetting or pruning

This is safe to do because only stale locks are removed. See restic/restic#2736 and https://github.com/restic/restic/blob/master/internal/restic/lock.go
By default only locks older than 30 minutes or when the pid is no longer found on the same machine, are removed. Locks are refreshed every 5 minutes when doing operations.

Author: lawndoc

src/restic_compose_backup/restic.py

@@ -77,6 +77,9 @@ def is_initialized(repository: str) -> bool:
 
 
 def forget(repository: str, daily: str, weekly: str, monthly: str, yearly: str):
+    commands.run(restic(repository, [
+        'unlock'
+    ])
     return commands.run(restic(repository, [
         'forget',
         '--group-by',
@@ -93,6 +96,9 @@ def forget(repository: str, daily: str, weekly: str, monthly: str, yearly: str):
 
 
 def prune(repository: str):
+    commands.run(restic(repository, [
+        'unlock'
+    ])
     return commands.run(restic(repository, [
         'prune',
     ]))