Thanks to the Chimera Programming FAQ, I've already managed to install BioPython succesfully on Ubuntu, but on Mac OS X I get the following error:

Error while importing Combine from /Applications/Chimera.app/Contents/Resources/share:

Traceback (most recent call last):

  File "/Applications/Chimera.app/Contents/Resources/share/chimera/extension/base.py", line 349, in _importExtension

    __import__(module)

  File "/Applications/Chimera.app/Contents/Resources/share/Combine/ChimeraExtension.py", line 32, in <module>

    balloon="Combine molecular models into new model", moleculesOnly=True)

  File "/Applications/Chimera.app/Contents/Resources/share/ModelPanel/base.py", line 40, in addButton

    "Button named '%s' already exists" % name

KeyError: "Button named 'copy/combine...' already exists"

Error while importing Ramachandran from /Applications/Chimera.app/Contents/Resources/share:

Traceback (most recent call last):

  File "/Applications/Chimera.app/Contents/Resources/share/chimera/extension/base.py", line 349, in _importExtension

    __import__(module)

  File "/Applications/Chimera.app/Contents/Resources/share/Ramachandran/ChimeraExtension.py", line 29, in <module>

    ModelPanel.addButton("Ramachandran plot...", emo.modelPanelCB)

  File "/Applications/Chimera.app/Contents/Resources/share/ModelPanel/base.py", line 40, in addButton

    "Button named '%s' already exists" % name

KeyError: "Button named 'Ramachandran plot...' already exists"

running install

running build

running build_py

running build_ext

Error while processing 'setup.py install':

TypeError: argument of type 'NoneType' is not iterable

  File "/Applications/Chimera.app/Contents/Resources/frameworks/Python.framework/Versions/2.7/lib/python2.7/_osx_support.py", line 185, in _find_appropriate_compiler

    if 'llvm-gcc' in data:

See reply log for Python traceback.