[postprocessor] update 'finalize' events

Add 'finalize-error' and 'finalize-success' events that trigger
depending on whether error(s) did or did not happen.

'finalize' itself now always triggers regardless of error status.
(was supposed to have the same behavior as the new 'finalize-success')

gallery_dl/postprocessor/exec.py

@@ -46,10 +46,7 @@ class ExecPP(PostProcessor):
 
         self._init_archive(job, options)
 
-    def exec_list(self, pathfmt, status=None):
-        if status:
-            return
-
+    def exec_list(self, pathfmt):
         archive = self.archive
         kwdict = pathfmt.kwdict
 
@@ -67,15 +64,12 @@ class ExecPP(PostProcessor):
         if archive:
             archive.add(kwdict)
 
-    def exec_string(self, pathfmt, status=None):
-        if status:
-            return
-
+    def exec_string(self, pathfmt):
         archive = self.archive
         if archive and archive.check(pathfmt.kwdict):
             return
 
-        if status is None and pathfmt.realpath:
+        if pathfmt.realpath:
             args = self.args.replace("{}", quote(pathfmt.realpath))
         else:
             args = self.args.replace("{}", quote(pathfmt.realdirectory))