distributor update fails trying to remove already-missing key
When a client wants to update a distributor config, they can remove a setting entirely from the config by passing a value of "None" as the value in the update call. This is documented in the REST API docs. Pulp sees the value of None and removes the corresponding key from the distributor's config.
But it assumes that key is present. If it is not, an unhandled KeyError exception occurs.
That line of code makes the assumption. The bug could be fixed by giving "pop()" a default value as the second argument.