title: list python package dependencies without loading them?
body: <p>Say that python package A requires B, C and D;
  is there a way to list A &rarr; B C D without loading them ?<br>
  <code>Requires</code> in the metadata (<code>yolk -M A</code>) are often incomplete, grr.<br>
  One can download A.tar / A.egg, then look through A/setup.py,
  but some of those are pretty gory.</p>
  
  <p>(I'd have thought that getting at least first-level dependencies could be mechanized;
  even a 98 % solution would be better than avalanching downloads.)</p>
  
  <p>A related question:
  <a href="https://stackoverflow.com/questions/2861183/pip-upgrade-package-without-upgrading-dependencies">pip-upgrade-package-without-upgrading-dependencies</a></p>