tldr: poetry2nix can't build django-anymail[postmark] version 10.1.
It seems like something in the build + installation chain tries to install an
extra I do not need where cryptography is needed and can't be built. The
machinery doesn't seem to listen to my instructions that it shouldn't install
any extras at all which is fascinating.
ERROR: Could not find a version that satisfies the requirement cryptography; sys_platform != "darwin" or platform_machine != "arm64" or python_version >= "3.9" and extra == "postal" (from django-anymail) (from versions: none)
ERROR: No matching distribution found for cryptography; sys_platform != "darwin" or platform_machine != "arm64" or python_version >= "3.9" and extra == "postal"
error: builder for '/nix/store/n4dcfphqn6187w567s97rh6k4ns36ia7-python3.10-django-anymail-10.1.drv' failed with exit code 1
error: 1 dependencies of derivation '/nix/store/2zp58aynr7xmnvz1ggbxp31r4ci6g7sd-python3.10-tmp-0.1.0.drv' failed to build
nix-shell
nix-build