apt_repository: Fix crash caused by cache.update() raising an IOError on timeout. (#51996)

* Fix crash caused by cache.update() raising an IOError on timeout.

* Add changelog fragment.

changelogs/fragments/51995-apt_repository-catch-IOError.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+  - apt_repository - Fix crash caused by ``cache.update()`` raising an ``IOError`` due to a timeout in ``apt update`` (https://github.com/ansible/ansible/issues/51995)

lib/ansible/modules/packaging/os/apt_repository.py

@@ -108,6 +108,7 @@ import os
 import re
 import sys
 import tempfile
+import copy
 
 try:
     import apt
@@ -515,6 +516,7 @@ def main():
     else:
         module.fail_json(msg='Module apt_repository is not supported on target.')
 
+    sourceslist_before = copy.deepcopy(sourceslist)
     sources_before = sourceslist.dump()
 
     try:
@@ -544,8 +546,16 @@ def main():
             if update_cache:
                 cache = apt.Cache()
                 cache.update()
-        except OSError as err:
+        except (OSError, IOError) as err:
-            module.fail_json(msg=to_native(err))
+            # Revert the sourcelist files to their previous state.
+            # First remove any new files that were created:
+            for filename in set(sources_after.keys()).difference(sources_before.keys()):
+                if os.path.exists(filename):
+                    os.remove(filename)
+            # Now revert the existing files to their former state:
+            sourceslist_before.save()
+            # Return an error message.
+            module.fail_json(msg='apt cache update failed')
 
     module.exit_json(changed=changed, repo=repo, state=state, diff=diff)