Xblock workbench and edx-platform don't easily coexist

If you go through the standard "devstack" setup of edx-platform, then do (in some other directory):

git clone https://github.com/edx/XBlock.git xblock
cd xblock
pip install -r requirements.txt

Then go back to platform, and do:

rake devstack[studio]

The following error results:

edxapp@precise64:~/edx-platform$ rake devstack[studio]
Node requirements unchanged, nothing to install
Ruby requirements unchanged, nothing to install
pip install -q --exists-action w -r requirements/edx/pre.txt
pip install -q --exists-action w -r requirements/edx/base.txt
  Could not find a tag or branch 'd89aae2a82f2b', assuming commit.
  Could not find a tag or branch '88ec8a011e481918fdc9d2682d4017c835acd8be', assuming commit.
  Could not find a tag or branch '41815e2ef1b0323f92900f8e60711b0f0c37766b', assuming commit.
  Could not find a tag or branch 'cccc3978ad2df82a78b6f9648fe2e9baddd22f88', assuming commit.
  Could not find a tag or branch '776973740bdaad83a3b029f96e415a7d1e8bec2f', assuming commit.
  Could not find a tag or branch 'd53fe0e81b623f084e91776bcf6369f8b7b63879', assuming commit.
  Could not find a tag or branch 'a1a3e76b269d15b7bbd11976d8aef63e1db6c4c2', assuming commit.
  Could not find a tag or branch 'e3d98f9455', assuming commit.
  Could not find a tag or branch '823a102e48', assuming commit.
  Could not find a tag or branch 'f0211d702d', assuming commit.
  Could not find a tag or branch 'bc6f1adbe439618162079f1004b2b3db3b6f8916', assuming commit.
  Could not find a tag or branch 'afef6647edb488afc471b0239ef8c4b0669e5fdf', assuming commit.
pip install -q --exists-action w -r requirements/edx/post.txt
xmodule_assets common/static/xmodule
./manage.py cms --settings devstack preprocess_assets --traceback 
Traceback (most recent call last):
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/core/management/base.py", line 217, in execute
    translation.activate('en-us')
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/utils/translation/__init__.py", line 105, in activate
    return _trans.activate(language)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/utils/translation/trans_real.py", line 194, in activate
    _active.value = translation(language)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/utils/translation/trans_real.py", line 183, in translation
    default_translation = _fetch(settings.LANGUAGE_CODE)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/utils/translation/trans_real.py", line 160, in _fetch
    app = import_module(appname)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/utils/importlib.py", line 35, in import_module
    __import__(name)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/contrib/admin/__init__.py", line 4, in <module>
    from django.contrib.admin.options import ModelAdmin, HORIZONTAL, VERTICAL
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/contrib/admin/options.py", line 8, in <module>
    from django.contrib.admin import widgets, helpers
ImportError: cannot import name widgets
asset preprocessing failed!
node_modules/.bin/coffee --compile `find lms/ cms/ common/ -type f -name *.coffee` 
edxapp@precise64:~/edx-platform$ 

However, this can be solved by doing:

pip uninstall XBlockWorkbench

Reproduce the standard devstack setup with XBlockWorkbench installed, then run rake devstack[studio] in edx-platform and inspect the failure during preprocess_assets. Review the requirements/edx/pre.txt, base.txt, and post.txt dependency installation steps; done means XBlock and edx-platform can coexist and the devstack command completes without requiring pip uninstall XBlockWorkbench.