do we want

./pants run <target...>

to have access to the pants environment? this excerpt from above:

pkg_resources.VersionConflict: (pycodestyle 2.4.0 (/home/cosmicexplorer/tools/pants/build-support/pants_dev_deps.venv/lib/python2.7/site-packages), Requirement.parse('pycodestyle<2.4.0,>=2.0.0'))

seems to imply the pants venv is interacting with the

PYTHONPATH

exposed to python binaries? because the target

src/python/pants/util:s3_log_aggregator_bin

i think shouldn't be getting anything from the pants venv? i could be way mistaken. in fact, that's probably wrong in that that python binary target depends on

3rdparty/python:future

, which is in

requirements.txt

and therefore probably taken from the pants venv intentionally (an except of the BUILD file):

python_library(
  name = 's3_log_aggregator',
  sources = ['s3_log_aggregator.py'],
  dependencies = [
    '3rdparty/python:future',
    '3rdparty/python:s3logparse'
  ]
)

python_binary(
  name = 's3_log_aggregator_bin',
  entry_point = 'pants.util.s3_log_aggregator',
  dependencies = [
    ':s3_log_aggregator'
  ]
)

Your inference here is off. If you look at the full log from above the failure is in pyprep.requirements which is upstream of run. If you PEX_VERBOSE=9 you'll see this issue is encountered when building up the pex environment that will later be used for the run.