Hi,

Thanks for reporting this.

I could investigate it and find the root of that problem, and it was a
custom function detecting which files need to be copied to "build"

--8<---------------cut here---------------start------------->8---
def find_package_data(
--8<---------------cut here---------------end--------------->8---
<https://github.com/django-compressor/django-compressor/blob/4.5.1/setup.py#L51C1-L52C1>

As package has no many dependent I could push it to master, after local build:

--8<---------------cut here---------------start------------->8---
> ./pre-inst-env guix build -P1 build python-django-compressor
guix build: computing dependents of package build@0.3.10...
/gnu/store/r5k54f35gdqrkwzdg5xp4433wwpg0ps4-build-0.3.10
/gnu/store/vimdx5lvf453591rc8d2f802nz32nx4j-cli-1.1.0
/gnu/store/mcp3d7jiljl6s63vwf0dqn99mv4sg0g4-xsd-4.0.0-doc
/gnu/store/lgpqmp9hjlva9cgxvm2x420jd8nwl4h5-xsd-4.0.0
/gnu/store/wrh3k5cwvp8dcx40bkd6583zrhd5w0w8-libxsd-frontend-2.0.0
/gnu/store/v0hdy25fxh6kpmjx90p0zsarncm5hq0n-python-django-compressor-4.5.1
--8<---------------cut here---------------end--------------->8---

Templates dirrectory is present in the built package now:
--8<---------------cut here---------------start------------->8---
> tree -d $(./pre-inst-env guix build python-django-compressor)/lib/
/gnu/store/v0hdy25fxh6kpmjx90p0zsarncm5hq0n-python-django-compressor-4.5.1/lib/
└── python3.10
    └── site-packages
        ├── compressor
        │   ├── contrib
        │   │   └── __pycache__
        │   ├── filters
        │   │   ├── cssmin
        │   │   │   └── __pycache__
        │   │   ├── jsmin
        │   │   │   └── __pycache__
        │   │   └── __pycache__
        │   ├── management
        │   │   ├── commands
        │   │   │   └── __pycache__
        │   │   └── __pycache__
        │   ├── offline
        │   │   └── __pycache__
        │   ├── parser
        │   │   └── __pycache__
        │   ├── __pycache__
        │   ├── templates
        │   │   ├── compressor
        │   │   │   └── __pycache__
        │   │   └── __pycache__
        │   ├── templatetags
        │   │   └── __pycache__
        │   ├── tests
        │   │   └── __pycache__
        │   └── utils
        │       └── __pycache__
        └── django_compressor-4.5.1.dist-info

32 directories
--8<---------------cut here---------------end--------------->8---

Pushed fixes to master as:
0879cb6f66 * master gnu: python-django-compressor: Fix Python package data.
8335f7b441 * gnu: python-django-compressor: Fix indentation.

--
Oleg