Before:
  call ale#assert#SetUpLinterTest('python', 'prospector')

After:
  call ale#assert#TearDownLinterTest()

Execute(Setting executable to 'pipenv' appends 'run prospector'):
  let g:ale_python_prospector_executable = 'path/to/pipenv'

  AssertLinter 'path/to/pipenv',
  \ ale#Escape('path/to/pipenv') . ' run prospector'
  \   .  '  --messages-only --absolute-paths --zero-exit --output-format json %s'