fix: reraise original exception and windows specific cleanup errors

* Basing on #243, we are having some difficulty with pygit2 Repository file
  handlers being open. in `pygit.py` we instantiate the Repository
  class, which holds references to `pack` and `.idx` git objects and
  keeps files open. If taf and cleanup is attempted from same subprocess,
  Repository handler won't be deleted, and cleanup error occurs. Calling
  manual garbage collection did not help. This
  seems to be a known issue throughout the git community, see [1] and
  [2].

  [1] - libgit2/pygit2#596
  [2] - gitpython-developers/GitPython#546

  Several workarounds were proposed by the community, but it seems that
  we can't fully replicate those workarounds. In [2] they attempt to
  workaround the issue by deleting git cache. That works for them
  because their git implementation has file handlers open in pure
  python, while we only do subprocess git calls.

  Our TODO: if these  windows specific error issues keep persisting, figure out how to
  garbage collect pygit2 Repository handler correctly.

  For now settle on error handling, as this issue is
  specific to a subprocess call that calls taf/updater. Though we should
  keep track of progress of these known bugs, so we can fix them if they
  get addressed by pygit2 or gitpython

Author: n-dusan

taf/updater/handlers.py

@@ -257,7 +257,15 @@ def cleanup(self):
         self.validation_auth_repo.cleanup()
         temp_dir = Path(self.validation_auth_repo.path, os.pardir).parent
         if temp_dir.is_dir():
-            shutil.rmtree(str(temp_dir), onerror=on_rm_error)
+            try:
+                shutil.rmtree(str(temp_dir), onerror=on_rm_error)
+            except (OSError, PermissionError) as e:
+                taf_logger.error(
+                    "Could not remove temporary directory {}. Error: {}",
+                    temp_dir,
+                    e,
+                )
+                raise e
 
     def earliest_valid_expiration_time(self):
         # Only validate expiration time of the last commit

taf/updater/updater.py

@@ -1278,7 +1278,7 @@ def _validate_authentication_repository(
     try:
         _update_authentication_repository(repository_updater)
     except Exception as e:
-        error_msg = e
+        error_msg = str(e)
 
     # this is the repository cloned inside the temp directory
     # we validate it before updating the actual authentication repository
@@ -1290,7 +1290,7 @@ def _validate_authentication_repository(
         and users_auth_repo.last_validated_commit is None
         and commits[0] != out_of_band_authentication
     ):
-        error_msg = UpdateFailedError(
+        error_msg = (
             f"First commit of repository {auth_repo_name} does not match "
             "out of band authentication commit"
         )
@@ -1305,22 +1305,25 @@ def _validate_authentication_repository(
         targets = validation_auth_repo.get_json(commits[-1], "metadata/targets.json")
         test_repo = "test-auth-repo" in targets["signed"]["targets"]
         if test_repo and expected_repo_type != UpdateType.TEST:
-            error_msg = UpdateFailedError(
+            error_msg = (
                 f"Repository {users_auth_repo.name} is a test repository. "
                 'Call update with "--expected-repo-type" test to update a test '
                 "repository"
             )
         elif not test_repo and expected_repo_type == UpdateType.TEST:
-            error_msg = UpdateFailedError(
+            error_msg = (
                 f"Repository {users_auth_repo.name} is not a test repository,"
                 ' but update was called with the "--expected-repo-type" test'
             )
 
     # always cleanup repository updater
-    repository_updater.update_handler.cleanup()
+    try:
+        repository_updater.update_handler.cleanup()
+    except Exception as e:
+        error_msg += f"Failed to cleanup repository updater: {str(e)}"
 
     return (
         commits,
-        error_msg,
+        UpdateFailedError(error_msg) if error_msg else None,
         last_validated_commit,
     )