RPM Support

The pulp-admin tool doesn't currently support uploading modular errata.
This requires enhancement of the --pkglist-csv packagelist.csv switch of the errata upload subcommand because at the moment there's no way to assign a package list to a modular erratum.
Possible solution might add a new, nargs switch that would accept a JSON structure, similar to the one the upload API uses, e.g:
$ pulp-admin rpm repo uploads erratum --repo-id zoo --erratum-id RHEA-2018:0042 ... --module-package-collection gorilla.json --module-package-collection walrus.json
$ cat walrus.json

  { "name": "collection 0",
      "short": "0",
      "module": {
        "name": "walrus",
        "stream": "5.21",
        "version": "20180704144203",
        "arch": "x86_64",
        "context": "deadbeef"
      },
      "packages": []
    }