the stack down to urllib is:

File "/usr/local/Cellar/python@2/2.7.14_3/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib.py", line 1462 in proxy_bypass_macosx_sysconf
  File "/usr/local/Cellar/python@2/2.7.14_3/Frameworks/Python.framework/Versions/2.7/lib/python2.7/urllib.py", line 1519 in proxy_bypass
  File "/Users/benjyw/.cache/pants/setup/bootstrap-Darwin-x86_64/1.8.0/lib/python2.7/site-packages/requests/utils.py", line 676 in should_bypass_proxies
  File "/Users/benjyw/.cache/pants/setup/bootstrap-Darwin-x86_64/1.8.0/lib/python2.7/site-packages/requests/utils.py", line 692 in get_environ_proxies
  File "/Users/benjyw/.cache/pants/setup/bootstrap-Darwin-x86_64/1.8.0/lib/python2.7/site-packages/requests/sessions.py", line 672 in merge_environment_settings
  File "/Users/benjyw/.cache/pants/setup/bootstrap-Darwin-x86_64/1.8.0/lib/python2.7/site-packages/requests/sessions.py", line 499 in request
  File "/Users/benjyw/.cache/pants/setup/bootstrap-Darwin-x86_64/1.8.0/lib/python2.7/site-packages/requests/api.py", line 58 in request
  File "/Users/benjyw/.cache/pants/setup/bootstrap-Darwin-x86_64/1.8.0/lib/python2.7/site-packages/requests/api.py", line 112 in post
  File "/Users/benjyw/.cache/pants/setup/bootstrap-Darwin-x86_64/1.8.0/lib/python2.7/site-packages/pants/goal/run_tracker.py", line 320 in post_stats
  File "/Users/benjyw/.cache/pants/setup/bootstrap-Darwin-x86_64/1.8.0/lib/python2.7/site-packages/pants/goal/run_tracker.py", line 371 in store_stats
  File "/Users/benjyw/.cache/pants/setup/bootstrap-Darwin-x86_64/1.8.0/lib/python2.7/site-packages/pants/goal/run_tracker.py", line 419 in end

... not sure if there is a code change that could avoid proxy usage