package does not exist; excluding resources

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I'm trying to convert pytz to use "proper" Python resources (see fork here, https://github.com/stub42/pytz/compare/master...ipmb:resource-loader) and having issues getting them picked up in pyoxidizer. If I install my package into a virtualenv and run with Python, it works as expected:

```
>>> import importlib.resources
>>> importlib.resources.read_binary("pytz.zoneinfo.Africa", "Accra")
b'TZif2\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\...
```

When I build the pyoxidizer binary, I see these warnings:

```
package pytz.zoneinfo.Africa does not exist; excluding resources: ["Abidjan", "Accra", "Addis_Ababa", "Algiers", "Asmara", "Asmera", "Bamako", "Bangui", "Banjul", "Bissau", "Blantyre", "Brazzaville", "Bujumbura", "Cairo", "Casablanca", "Ceuta", "Conakry", "Dakar", "Dar_es_Salaam", "Djibouti", "Douala", "El_Aaiun", "Freetown", "Gaborone", "Harare", "Johannesburg", "Juba", "Kampala", "Khartoum", "Kigali", "Kinshasa", "Lagos", "Libreville", "Lome", "Luanda", "Lubumbashi", "Lusaka", "Malabo", "Maputo", "Maseru", "Mbabane", "Mogadishu", "Monrovia", "Nairobi", "Ndjamena", "Niamey", "Nouakchott", "Ouagadougou", "Porto-Novo", "Sao_Tome", "Timbuktu", "Tripoli", "Tunis", "Windhoek"]
```

...and trying to run the binary, I get:

```
File "pytz", line 1115, in
File "pytz.lazy", line 101, in _lazy
File "pytz", line 1112, in
File "pytz", line 128, in resource_exists
File "pytz", line 106, in open_resource
File "importlib.resources", line 88, in open_binary
File "importlib.resources", line 49, in _get_package
TypeError: 'pytz.zoneinfo.Africa' is not a package
```

I'm using pyoxidizer version 0.2.0

Reproduce the failure with pytz, importlib.resources.read_binary("pytz.zoneinfo.Africa", "Accra"), and PyOxidizer 0.2.0. Start by tracing PyOxidizer's package resource discovery for pytz.zoneinfo.Africa and compare it with the virtualenv behavior. Done means the package is recognized, its zoneinfo resources are included, and the built binary runs without the TypeError.

Written by the indexing model from the issue text.