title: Python generate sdist and upload it in a separate step
body: <p>I am building several Python packages and would like to upload them only if all the packages have been successfully built. I have a separate stage for each Python package, whose <code>sdist</code> is carried to the last stage where all collected <code>sdist</code>s should be uploaded (if the build reaches the final stage, then all packages were built successfully).</p>
  
  <p>Now, is there a way to execute <code>python setup.py sdist</code>, then <code>python setup.py upload [path]</code> in order to achieve what I need? Or is there a better way for this?</p>
  
  <p>P.S.: I am using Bamboo, if it helps.</p>