D'oh - setup.py used the dict directly: make it use the wrapper function.

setup.py

@@ -45,7 +45,7 @@ setup(
     version=version,
     packages=find_packages(exclude=["tests", "tests.*"]),
     description="Reference Synapse Home Server",
-    install_requires=dependencies["REQUIREMENTS"].keys(),
+    install_requires=dependencies['requirements'](include_conditional=True).keys(),
     setup_requires=[
         "Twisted==14.0.2", # Here to override setuptools_trial's dependency on Twisted>=2.4.0
         "setuptools_trial",