[Nix-dev] buildPythonPackage: add src to PYTHONPATH before build?

[Jeffrey David Johnson]

I'm trying to package a python application (https://github.com/dagraham/etm-tk).
I made an initial package with python2nix, but when I try to install it I get:

installing ‘python2.7-etm’
these derivations will be built:
  /nix/store/a1xn163ms6rg3w9k901lr6fga4lawqx9-python2.7-etm.drv
building path(s) ‘/nix/store/bncc469m7v8r5i11ak9my9dxdjvm6cpg-python2.7-etm’
unpacking sources
unpacking source archive /nix/store/jdhl79isbzapyyz6vlh22i03m9lbc00w-etm-tk-7b6ba79
source root is etm-tk-7b6ba79
patching sources
configuring
building
Traceback (most recent call last):
  File "setup.py", line 3, in <module>
    from etmTk.v import version
ImportError: No module named etmTk.v
builder for ‘/nix/store/a1xn163ms6rg3w9k901lr6fga4lawqx9-python2.7-etm.drv’ failed with exit code 1
error: build of ‘/nix/store/a1xn163ms6rg3w9k901lr6fga4lawqx9-python2.7-etm.drv’ failed

How should I handle the setup.py importing a module from inside the package?
I imagine there's a hook somewhere where I could add it to the PYTHONPATH?
Jeff