While working on reproducible builds for openSUSE, I found that
osc build --vm-type=kvm -j1 --noservice
for python-nbconvert fails 1 test on a 1-core VM

1 failed, 251 passed, 32 skipped, 2 deselected, 59 warnings in 241.06


 =================================== FAILURES ==========================
 ________________________ TestExecute.test_disable_stdin ______________

 self = <nbconvert.preprocessors.tests.test_execute.TestExecute testMethod=test_
disable_stdin>

     def test_disable_stdin(self): 
         """Test disabling standard input"""
         filename = os.path.join(current_dir, 'files', 'Disable Stdin.ipynb')
         res = self.build_resources()
         res['metadata']['path'] = os.path.dirname(filename)
 >       input_nb, output_nb = self.run_notebook(filename, dict(allow_errors=True), res)



If you cannot debug this yourself, please work with upstream.