v1.10.0 is breaking JupyterLab CI

[fcollonval]

The error arises from:

jupyter_server/jupyter_server/utils.py

Line 391 in b4b1517

spec = importlib.util.find_spec(namespace)

From the documentation

Find the spec for a module, optionally relative to the specified package name. If the module is in sys.modules, then sys.modules[name].spec is returned (unless the spec would be None or is not set, in which case ValueError is raised).

If the application is defined in a Python file not belonging to a package, __spec__ won't be set - this is the case of the broken JupyterLab CI test.

Xref: jupyterlab/jupyterlab#10682