The ISOImporter performs some validation checks on uploaded ISOs, and if those validation checks fail, it raises a ValueError. Unfortunately, Pulp doesn't offer any way for Importers to indicate that they don't wish to accept an upload due to such problems, and the ValueError is not handled gracefully leading to a poor user experience.

For example, if a user tries to upload an ISO called PULP_MANIFEST (which is disallowed as of bug #973678), the upload will be unsuccessful, but the user will not see the error message that indicates why at the client.

$ pulp-admin iso repo uploads upload --repo-id test -f PULP_MANIFEST 
+----------------------------------------------------------------------+
                              Unit Upload
+----------------------------------------------------------------------+

Extracting necessary metadata for each request...
[==================================================] 100%
Analyzing: PULP_MANIFEST
... completed

Creating upload requests on the server...
[==================================================] 100%
Initializing: PULP_MANIFEST
... completed

Starting upload of selected units. If this process is stopped through ctrl+c,
the uploads will be paused and may be resumed later using the resume command or
cancelled entirely using the cancel command.

Uploading: PULP_MANIFEST
... completed

Importing into the repository...
The web server reported an error trying to access the Pulp application. The
likely cause is that the pulp-manage-db script has not been run prior to
starting the server. More information can be found in Apache's error log file on
the server itself.

It is also unhelpful that our default error message for unhandled exceptions tells the user that they probably need to run pulp-manage-db. From our pulp.log:

2013-09-05 11:31:23,073 pulp.server.managers.content.upload:ERROR: Error from the importer while importing uploaded unit to repository [test]
Traceback (most recent call last):
  File "/home/rbarlow/devel/pulp/server/pulp/server/managers/content/upload.py", line 227, in import_uploaded_unit
    importer_instance.upload_unit(transfer_repo, unit_type_id, unit_key, unit_metadata, file_path, conduit, call_config)
  File "/home/rbarlow/devel/pulp_rpm/pulp_rpm/src/pulp_rpm/plugins/importers/iso_importer/importer.py", line 129, in upload_unit
    iso.validate(full_validation=validate)
  File "/home/rbarlow/devel/pulp_rpm/pulp_rpm/src/pulp_rpm/common/models.py", line 409, in validate
    raise ValueError(msg)
ValueError: An ISO may not be named PULP_MANIFEST, as it conflicts with the name of the manifest during publishing.

It would be nice to provide that error message to the end user.