bump virtualenv version to 12.0.5
bump virtualenv version to 12.0.5

1.11.6 bundles a version of pip that has a bad implementation of uninstall_rollback which causes problems with certain types of resolvable dependency conflicts. Attempting to create the venv fails in a place where it isn't possible to fix easily because the file containing the bug is wiped out during venv creation.

This is the cause of:

  Exception:
  Traceback (most recent call last):
    File "~/oss/pants/build-support/pants_dev_deps.venv/lib/python2.7/site-packages/pip/basecommand.py", line 122, in main
      status = self.run(options, args)
    File "~/oss/pants/build-support/pants_dev_deps.venv/lib/python2.7/site-packages/pip/commands/install.py", line 283, in run
      requirement_set.install(install_options, global_options, root=options.root_path)
    File "~/oss/pants/build-support/pants_dev_deps.venv/lib/python2.7/site-packages/pip/req.py", line 1439, in install
      requirement.rollback_uninstall()
    File "~/oss/pants/build-support/pants_dev_deps.venv/lib/python2.7/site-packages/pip/req.py", line 603, in rollback_uninstall
      self.uninstalled.rollback()
    File "~/oss/pants/build-support/pants_dev_deps.venv/lib/python2.7/site-packages/pip/req.py", line 1855, in rollback
      pth.rollback()
  AttributeError: 'str' object has no attribute 'rollback'

  Storing debug log for failure in ~/.pip/pip.log

  Failed to install requirements from ~/oss/pants/3rdparty/python/requirements.txt.

Testing Done:
ran ./pants with PANTS_DEV=1 with this change and saw venv creation succeed

Reviewed at https://rbcommons.com/s/twitter/r/1621/

kwlzn/pants,dgomez10/xanon,foursquare/pants,kslundberg/pants,dturner-tw/pants,jessrosenfield/pants,lahosken/pants,tdyas/pants,gmalmquist/pants,baroquebobcat/pants,tdyas/pants,di0spyr0s/pants,lahosken/pants,qma/pants,peiyuwang/pants,TansyArron/pants,pgroudas/pants,pantsbuild/pants,lahosken/pants,fkorotkov/pants,megaserg/pants,benjyw/pants,baroquebobcat/pants,pombredanne/pants,kwlzn/pants,gmalmquist/pants,digwanderlust/pants,twitter/pants,mateor/pants,jtrobec/pants,kwlzn/pants,digwanderlust/pants,lahosken/pants,scode/pants,dbentley/pants,cevaris/pants,ericzundel/pants,UnrememberMe/pants,kslundberg/pants,dgomez10/xanon,mateor/pants,wisechengyi/pants,mateor/pants,15Dkatz/pants,digwanderlust/pants,peiyuwang/pants,lahosken/pants,wisechengyi/pants,UnrememberMe/pants,TansyArron/pants,twitter/pants,qma/pants,lahosken/pants,jessrosenfield/pants,laurentgo/pants,ericzundel/pants,mateor/pants,slyphon/pants,slyphon/pants,UnrememberMe/pants,slyphon/pants,areitz/pants,foursquare/pants,TansyArron/pants,dbentley/pants,jsirois/pants,dgomez10/xanon,dturner-tw/pants,landism/pants,Gabriel439/pants,dturner-tw/pants,jessrosenfield/pants,tejal29/pants,dbentley/pants,wisechengyi/pants,sameerparekh/pants,jtrobec/pants,digwanderlust/pants,dgomez10/xanon,Gabriel439/pants,wisechengyi/pants,pombredanne/pants,lahosken/pants,UnrememberMe/pants,slyphon/pants,Gabriel439/pants,ity/pants,cevaris/pants,peiyuwang/pants,kwlzn/pants,pantsbuild/pants,pombredanne/pants,15Dkatz/pants,wisechengyi/pants,sid-kap/pants,slyphon/pants,scode/pants,manasapte/pants,manasapte/pants,tdyas/pants,peiyuwang/pants,areitz/pants,gmalmquist/pants,benjyw/pants,benjyw/pants,twitter/pants,qma/pants,benjyw/pants,tdyas/pants,15Dkatz/pants,cevaris/pants,di0spyr0s/pants,dturner-tw/pants,TansyArron/pants,twitter/pants,UnrememberMe/pants,twitter/pants,tejal29/pants,ericzundel/pants,fkorotkov/pants,tejal29/pants,jtrobec/pants,jtrobec/pants,wisechengyi/pants,gmalmquist/pants,benjyw/pants,peiyuwang/pants,pgroudas/pants,15Dkatz/pants,sameerparekh/pants,twitter/pants,ericzundel/pants,kslundberg/pants,ericzundel/pants,areitz/pants,megaserg/pants,sameerparekh/pants,pantsbuild/pants,jessrosenfield/pants,pantsbuild/pants,tejal29/pants,kslundberg/pants,Gabriel439/pants,areitz/pants,pgroudas/pants,di0spyr0s/pants,cevaris/pants,tdyas/pants,baroquebobcat/pants,pgroudas/pants,fkorotkov/pants,twitter/pants,laurentgo/pants,fkorotkov/pants,jtrobec/pants,sid-kap/pants,megaserg/pants,ity/pants,Gabriel439/pants,dturner-tw/pants,cevaris/pants,kwlzn/pants,sid-kap/pants,dbentley/pants,areitz/pants,Gabriel439/pants,lahosken/pants,digwanderlust/pants,pantsbuild/pants,scode/pants,peiyuwang/pants,wisechengyi/pants,15Dkatz/pants,jessrosenfield/pants,dgomez10/xanon,scode/pants,sid-kap/pants,pombredanne/pants,UnrememberMe/pants,laurentgo/pants,slyphon/pants,tejal29/pants,jessrosenfield/pants,15Dkatz/pants,qma/pants,sameerparekh/pants,jsirois/pants,gmalmquist/pants,wisechengyi/pants,manasapte/pants,cevaris/pants,benjyw/pants,foursquare/pants,qma/pants,foursquare/pants,manasapte/pants,baroquebobcat/pants,TansyArron/pants,sameerparekh/pants,ity/pants,scode/pants,ity/pants,pombredanne/pants,dgomez10/xanon,scode/pants,landism/pants,jtrobec/pants,landism/pants,baroquebobcat/pants,wisechengyi/pants,ity/pants,foursquare/pants,pantsbuild/pants,sameerparekh/pants,sid-kap/pants,gmalmquist/pants,landism/pants,kwlzn/pants,scode/pants,twitter/pants,qma/pants,ericzundel/pants,megaserg/pants,megaserg/pants,baroquebobcat/pants,pombredanne/pants,tdyas/pants,peiyuwang/pants,dbentley/pants,ericzundel/pants,tdyas/pants,megaserg/pants,jtrobec/pants,Gabriel439/pants,jsirois/pants,pantsbuild/pants,UnrememberMe/pants,sid-kap/pants,areitz/pants,jessrosenfield/pants,laurentgo/pants,ity/pants,pgroudas/pants,peiyuwang/pants,twitter/pants,laurentgo/pants,UnrememberMe/pants,di0spyr0s/pants,baroquebobcat/pants,ity/pants,fkorotkov/pants,di0spyr0s/pants,mateor/pants,di0spyr0s/pants,dgomez10/xanon,landism/pants,dturner-tw/pants,sameerparekh/pants,digwanderlust/pants,fkorotkov/pants,TansyArron/pants,cevaris/pants,TansyArron/pants,manasapte/pants,foursquare/pants,mateor/pants,dgomez10/xanon,dgomez10/xanon,dgomez10/xanon,manasapte/pants,tdyas/pants,UnrememberMe/pants,areitz/pants,manasapte/pants,fkorotkov/pants,sid-kap/pants,dbentley/pants,kwlzn/pants,foursquare/pants,mateor/pants,dgomez10/xanon,qma/pants,gmalmquist/pants,landism/pants,15Dkatz/pants,ericzundel/pants,benjyw/pants,baroquebobcat/pants,megaserg/pants,pombredanne/pants,tdyas/pants,laurentgo/pants,pgroudas/pants,kslundberg/pants,foursquare/pants,15Dkatz/pants,landism/pants,kslundberg/pants,dturner-tw/pants,landism/pants,mateor/pants,baroquebobcat/pants,di0spyr0s/pants,foursquare/pants,fkorotkov/pants,dbentley/pants,slyphon/pants,kslundberg/pants