old_contents: project_slug = '{{ cookiecutter.project_slug }}'
  
  print('pre gen')
  
  if hasattr(project_slug, 'isidentifier'):
      assert project_slug.isidentifier(), 'Project slug should be valid Python identifier!'
  
new_contents: project_slug = '{{ cookiecutter.project_slug }}'
  
  
  if hasattr(project_slug, 'isidentifier'):
      assert project_slug.isidentifier(), 'Project slug should be valid Python identifier!'
  
subject: Fix a typo in the pre-generation hooks