old_contents: # content of conftest.py
  import pytest
  
  def pytest_addoption(parser):
      parser.addoption("--uchime-ref-db-fp", action="store",  help="path to PR2 database")
  
  @pytest.fixture
  def uchime_ref_db_fp(request):
      return request.config.getoption("--uchime-ref-db-fp")
  
new_contents: # content of conftest.py
  import pytest
  
  def pytest_addoption(parser):
      parser.addoption("--uchime-ref-db-fp", action="store", required=True, help="path to PR2 database")
  
  @pytest.fixture
  def uchime_ref_db_fp(request):
      return request.config.getoption("--uchime-ref-db-fp")
  
subject: make test option --uchime-ref-db-fp required