AttributeError: 'NoneType' object has no attribute 'loader'

I have built a PyOxidizer project and when I run the executable file I get the following error:
```
AttributeError: 'NoneType' object has no attribute 'loader'
error: cargo run failed
```
Can someone suggest what I can do to get more information, perhaps an option for `pyoxidizer run` that provides more verbose output?

My `pyoxidizer.toml` file:
```
[[build]]
application_name = "deep_monitor"

[[embedded_python_config]]
raw_allocator = "jemalloc"

[[embedded_python_config]]
build_target = "x86_64-pc-windows-msvc"
raw_allocator = "system"

[[packaging_rule]]
type = "stdlib-extensions-policy"
policy = "all"

[[packaging_rule]]
type = "stdlib"
include_source = false

[[packaging_rule]]
type = "write-license-files"
path = ""

[[packaging_rule]]
type = "virtualenv"
path = "/home/james/.virtualenvs/pyox"

[[embedded_python_run]]
mode = "module"
module = "deep_monitor"

[[python_distribution]]
build_target = "x86_64-apple-darwin"
url = "https://github.com/indygreg/python-build-standalone/releases/download/20190617/cpython-3.7.3-macos-20190618T0523.tar.zst"
sha256 = "6668202a3225892ce252eff4bb53a58ac058b6a413ab9d37c026a500c2a561ee"
[[python_distribution]]
build_target = "x86_64-pc-windows-msvc"
url = "https://github.com/indygreg/python-build-standalone/releases/download/20190617/cpython-3.7.3-windows-amd64-20190618T0516.tar.zst"
sha256 = "fd43554b5654a914846cf1c251d1ad366f46c7c4d20b7c44572251b533351221"
[[python_distribution]]
build_target = "x86_64-unknown-linux-gnu"
url = "https://github.com/indygreg/python-build-standalone/releases/download/20190617/cpython-3.7.3-linux64-20190618T0324.tar.zst"
sha256 = "d6b80a9723c124d6d193f8816fdb874ba6d56abfb35cbfcc2b27de53176d0620"
[[python_distribution]]
build_target = "x86_64-unknown-linux-musl"
url = "https://github.com/indygreg/python-build-standalone/releases/download/20190617/cpython-3.7.3-linux64-musl-20190618T0400.tar.zst"
sha256 = "2be2d109b82634b36685b89800887501b619ef946dda182e5a8ab5c7029a8136"

[[pyoxidizer]]
version = "0.2.0"
commit = ""
```

Thanks in advance for any comments or suggestions.

Start with pyoxidizer.toml and the executable produced by pyoxidizer run; capture the full traceback or verbose output around the NoneType loader error. Done means identifying whether the configuration or runtime packaging causes the failure and documenting a reproducible fix.

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