Changes requested: use Exception in db.close(), change minimum version, add a method to test for existence of LibraryClosed plugins.

Note that the plugins cannot actually be tested with this commit because calibre's version is 2.53.

src/calibre/customize/__init__.py

@@ -789,8 +789,8 @@ class LibraryClosedPlugin(Plugin):  # {{{
     '''
     type = _('Library Closed')
 
-    # minimum version 2 because it requires the new db
-    minimum_calibre_version = (2, 0, 0)
+    # minimum version 2.54 because that is when support was added
+    minimum_calibre_version = (2, 54, 0)
 
     def run(self, db):
         '''

src/calibre/customize/ui.py

@@ -255,6 +255,13 @@ def available_library_closed_plugins():
             if not is_disabled(plugin):
                 plugin.site_customization = customization.get(plugin.name, '')
                 yield plugin
+
+def has_library_closed_plugins():
+    for plugin in _initialized_plugins:
+        if isinstance(plugin, LibraryClosedPlugin):
+            if not is_disabled(plugin):
+                return True
+    return False
 # }}}
 
 # Store Plugins # {{{

src/calibre/db/cache.py

@@ -2017,7 +2017,7 @@ class Cache(object):
         for plugin in available_library_closed_plugins():
             try:
                 plugin.run(self)
-            except:
+            except Exception:
                 import traceback
                 traceback.print_exc()
         self.backend.close()

src/calibre/gui2/ui.py

@@ -880,8 +880,8 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin,  # {{{
     def shutdown(self, write_settings=True):
         get_gui().show_shutdown_message(_('Shutting down'))
 
-        from calibre.customize.ui import available_library_closed_plugins
-        if available_library_closed_plugins():
+        from calibre.customize.ui import has_library_closed_plugins
+        if has_library_closed_plugins():
             get_gui().show_shutdown_message(
                 _('Running database shutdown plugins. This could take a few seconds...'))