pep517 based build fails with
```console
+ /usr/bin/python3 -sBm build -w --no-isolation
* Getting build dependencies for wheel...
[numcodecs] setting up Blosc extension
[numcodecs] compiling Blosc extension with SSE2 support
Traceback (most recent call last):
File "/usr/lib/python3.8/site-packages/pyproject_hooks/_in_process/_in_process.py", line 353, in
main()
File "/usr/lib/python3.8/site-packages/pyproject_hooks/_in_process/_in_process.py", line 335, in main
json_out['return_val'] = hook(**hook_input['kwargs'])
File "/usr/lib/python3.8/site-packages/pyproject_hooks/_in_process/_in_process.py", line 118, in get_requires_for_build_wheel
return hook(config_settings)
File "/usr/lib/python3.8/site-packages/setuptools/build_meta.py", line 325, in get_requires_for_build_wheel
return self._get_build_requires(config_settings, requirements=['wheel'])
File "/usr/lib/python3.8/site-packages/setuptools/build_meta.py", line 295, in _get_build_requires
self.run_setup()
File "/usr/lib/python3.8/site-packages/setuptools/build_meta.py", line 311, in run_setup
exec(code, locals())
File "", line 305, in
File "", line 287, in run_setup
File "", line 69, in blosc_extension
UnboundLocalError: local variable 'blosc_sources' referenced before assignment
ERROR Backend subprocess exited when trying to invoke get_requires_for_build_wheel
```
Looks like something os wrong and ..
pep517 based build fails with
```console + /usr/bin/python3 -sBm build -w --no-isolation * Getting build dependencies for wheel... [numcodecs] setting up Blosc extension [numcodecs] compiling Blosc extension with SSE2 support Traceback (most recent call last): File "/usr/lib/python3.8/site-packages/pyproject_hooks/_in_process/_in_process.py", line 353, in