In reply to @jtojnar:matrix.org
That looks fine. Maybe the environment contamination comes from ambient environment then.

Here's the log:

$ setzer 

(process:29915): Gtk-WARNING **: 19:00:13.081: Locale not supported by C library.
	Using the fallback 'C' locale.
Fontconfig error: Cannot load default config file: No such file: (null)
Traceback (most recent call last):
  File "/nix/store/g6l9y20628gridb0g2kypvn2n4m5rdfd-setzer-62/bin/..setzer-wrapped-wrapped", line 28, in <module>
    from setzer.workspace.workspace import Workspace
  File "/nix/store/g6l9y20628gridb0g2kypvn2n4m5rdfd-setzer-62/lib/python3.11/site-packages/setzer/workspace/workspace.py", line 26, in <module>
    import setzer.document.preview.preview as preview
  File "/nix/store/g6l9y20628gridb0g2kypvn2n4m5rdfd-setzer-62/lib/python3.11/site-packages/setzer/document/preview/preview.py", line 31, in <module>
    import setzer.document.preview.preview_presenter as preview_presenter
  File "/nix/store/g6l9y20628gridb0g2kypvn2n4m5rdfd-setzer-62/lib/python3.11/site-packages/setzer/document/preview/preview_presenter.py", line 21, in <module>
    import cairo
  File "/nix/store/m69f7w3q03ihr9a34ajbm872k2na5xr8-python3.10-pycairo-1.24.0/lib/python3.10/site-packages/cairo/__init__.py", line 1, in <module>
    from ._cairo import *  # noqa: F401,F403
    ^^^^^^^^^^^^^^^^^^^^^
ModuleNotFoundError: No module named 'cairo._cairo'