i figured out the above it was because i was assuming too much of

pants_requirement()

-- it covers plugins with the

plugins

entry in pants.ini, but not mere python subpackages such as e.g.

pantsbuild.pants.testinfra

. i ended up making a context-aware object factory to cover pulling in

'pantsbuild.pants.testinfra=={}'.format(pants_version())

into a single

python_requirement_library()

along with pants because that seemed convenient for me